Most of these bugs related with engine working. Game is a mod to Half-life, so all these bugs working there too. 
#1. Bomb falls down into box. This bug is working if you plant bomb on player. In so doing, model of bomb can move through player's model. Green boxes on plant A are models too. One of these boxes leaned so if the player sit on it then one his leg appears inside the box. While falling in player's model, bomb can leave this model inside the model of box, further it will fall through box. 
#2. Acceleration on ladder. Game engine defines move speed to each move-key separately. If you press two keys (not beyond each other) then while directing view to middle of two directions which relevant each move key you will get overlap of velocities ladder moving. 
#3. Falling to corner. If while player's flying two walls located by acute angle block him then player stops to fall. This can be used for saving health while falling from big height. 
#4. Surfing. Player can climb to even steep slope. But, in so doing, speed of climbing depends on angle and moving direction. If you on middle of slope changes moving direction by mouse then you slides to side with good acceleration while gradually loosing height. 
#5. Close door from other side. While hitting door one more time we closes it, but it's possible from any side, even by hitting an edge of door. 
#6. OB. Object boost. At the time of pressing "use" on any movable object, game stops player and prevent increasing his speed. But at the little moment while pressing use with moving, object get huge acceleration and briefly make link with player. If you catch the moment when object has already got big speed but link has not broken yet, and release "use" then player quickly move to same direction as object. 
#7. 4x fire glock. During shooting in single-mode we can press right mouse key with not releasing left one. In so doing shooting mode will be changed. In 3x-fire mode pistol can shoot continuously with pressed left mouse key. So if during pressed LMK it immediately make shot and it looks like 4x fire. 
#8. Push player to ceiling, Dust. While sitting player's model is unstable. So if you climb onto sitting player then you get some little buzzing. If these two players locate in place with low thin ceiling and starts to repeatedly jump then at the moment when upper player jump off from lower one in top point, for a little time model of upper player appears in texture too deeply. After that game consider that player locates over texture and immediately move him to valid location.
#9. Push player to ceiling, booth Nuke. Similar to #8
#10. Push player to ceiling, roof Nuke. Similar to #8
#11. Smoke stuck and flied away. Grenades while hitting a slope uses to stick on it for a long time. HE and flash grenades explodes after several seconds at any case but smoke grenade explodes only after coming to stable position. Therefore, stuck grenade locates on texture for a long time and then texture strongly push it out.
#12. Smoke stuck. Based on #11. In the case that leaned texture locates near other vertical surface, texture can not push grenade. Consequently, it stays there for all round. 
#13. Gap on Inferno. To prevent overlap of textures, developers often set pixel between box and floor. In this case you can see and use it. 
#14. FB. Flash bug. Based on #13. If flash grenade get stuck in this gap then it explodes in texture in fact. So texture now can blind, i.e. box. In so doing you does not hear any sound.
#15. Soundless plant. Source of sound in bomb locates in not the middle of model but in corner. If we plant the bomb the way that this corner will appear in texture, then it will stop to make sound. That is not working on green boxes because it's models on this map. 
#16. Soundless defusing. In the game engine doesn't allow to play some sounds simultaneously. Such as sounds of flashlight, knife blow, optics, defusing. So after actuating one sound if we immediately actuate other one, so first will be stopped. If you make it enough quickly, enemy will not hear defusing sound. 
#17. Perpetual motion machine. Similar to #11.
#18. Spectacular throwing smoke to respawn. Similar to #11
#19. See through wall Dust2 T. Some textures which crossing with small angle each other, allows player's view to little move into the texture. That's allow to see a little through the texture. For this you need to snuggle to this crossing and move the view to the way that it will appear on the edge of screen and crossing line should be exactly vertical on screen.
#20. See through wall Dust2 box. Similar to #19.
#21. Matrix jump. Any animation which actuating in beginning or during jump, staying to the end of jump. You see, let's name it, zero animation. It occurs if game tries to execute animation which is not provided. Such moment occurs if we switch weapon while reloading. On ground this is happens so quick that we not notice it. But using the sticky animation effect, we can see it for all time of jump. Best working if switch to the bomb. 
#22. breaking doors, Nuke. For some reason developers made separately glasses and doors models. Additionally, they added same scripts separately to glasses and doors. It works by both same triggers. At the time of opening the triggers moves too. If, while this moving, you by sitting will jump to edge of this door then there is a chance that only one trigger will work. This means that glass will separate from door and now it will move without dependence from each other. 
#23. Hide by ledges. Sitting model of player, with grenade and certain angle to wall, is considerably shifts to wall. So it's invisible behind ledge. But using of nonstandard models is cause of useless of this trick. 
#24. Defusing by walking. After actuating optics, player get new params of speed of walking, running or crawling. When player defuses bomb, game set to him zero params of speed, but developers did not take account that actuating optics set new params even while defusing. 
Strafe.  - Simultaneously pressing side move key and moving mouse to same side in the air. It allows to increase horizontal speed almost limitless. more speed of mouse moving (by certain limit) - more acceleration. 
Pre. Prestrafe - Strafing with pressed forward key on ground. By using prestrafe we can increase horizontal speed on ground to 277 unit/sec.
#25. BHop. Bunny hop. Based on Strafe. At the time of landing game pulls over player in order for not be able to quick continuously jumping. But if you jump off at the moment of landing at once, you don't lose speed, mouse wheel allows to jump off immediately because it gives big amount of jump commands for little time. Also script with several jump commands can help you in this case, for example to RMB: bind mouse2 ";+jump;wait;-jump;wait;+jump;wait;-jump;wait;+jump;wait;-jump;wait;+jump;wait;-jump;wait;+jump;wait;-jump;wait;+jump;wait;-jump". By good strafes you can offset small mistakes of landing and even move faster than usual running. You should take into account that second and further jumps have some smaller height than first, so, time for strafes is smaller too. Also if you increased speed more than 300 units/sec, game, in any case, pulls over player to about 250 unit/sec and lower.  
#26. JB. Jump bug. Sitting model of player has smaller height. after releasing "duck" model immediately lines up. If at this moment you jump from ground then game can miss the moment of landing and health will not decreased. This point in time is so small that probability of executing bug is extremely low. Also it decreases by height. 
#27. EB. Edge bug. At the time of landing player can loose speed by edge of any horizontal texture. If player immediately will continue the flight then game may not react to landing and not decrease health. 
#28. Run with scout. Added feature from developers. Running with scout increases speed on 10 unit/sec. 
#29. FR. Fastrun. Based on Pre. Using short-term prestrafe elements many times, we can increase average speed of running on 10 units/sec. 
#30. WR. Wall rub. Based on Pre. If we snuggling and running along the wall, with certain angle to wall, speed can reach max of prestrafe. 
#31. SJ. Strafe jump. Based on Strafe, Pre. Using prestrafe and one strafe you can hug impediments while jumping, by pre speed and acceleration by strafe. 
#32. LJ. Long jump. Based on Strafe, Pre, #31. Making at least two strafes you can line up the trajectory of jump and increase jump speed. So this way you increases length of jump. More strafes, closer to ideal trajectory and longer jump. 
#33. HJ. High jump. Based on Strafe, Pre, #32. Same long jump but on height. If player run on edge of flat, located on good height, game pull over player, and make jump ineffective. But if you jumps about 10 units in advance, that will be normal.
#34. BHJ. Bunny hop jump. Based on Strafe, Pre, #25, #32. Combination of Bhop and LJ
#35. WJ. Weird jump. Based on Strafe, Pre, #25, #32. Using short-term falling for increasing speed before jump, we get best alternate of prestrafe with pre speed right up to 299. Also jump has normal height unlike bhop so length will be much more. 
#36. DD. Double duck. After short-term sitting model of player jumps. If, in so doing, press duck one time more, then you can jump on low object almost without loosing of speed.
#37. SR. Silent run. Based on #36. At the time of Double duck if we don't release second duck, then we have significant time to landing. If you continuously making it then sound of run becomes much quieter.
#38. DDR. Double duck run. Based on Strafe, #36. At the time of DD jump we have little time to use strafes. Extremely difficult trick, difficulty of it means that exact guessing of moments of landing after each DD. Increasing of speed take much time but only one landing mistake can eat almost all your speed. Using this trick you can run much faster than usual running. Also game don't limit speed after 300 u/s while landing as in BHop. 
SGS. Stand-up ground strafe. Based on Strafe, #36, #37, #38. Trick like DDR, but after each DD pressing duck (on keyboard) one more like in Silent run. Increased time terms before landing, unlike DDR, allows to make more strafes. Servers with increased air acceleration (100aa) allow to make it effectively.  
#39. CJ. Count jump. Based on Strafe, Pre, #31, #32, #36, #38. Using one ore more DDR tricks as a prestrafe, we can jump much farther than in any other kind of jump. 
SCJ. Stand-up count jump. Based on Strafe, Pre, #31, #32, #36, #37, #38, SGS. Difference of this CJ is using SGS trick instead DDR. 
#40. DJ. Duck jump. Jump with sitting at one time. Due to lower model of player in sitting state, you can jump in places with low ceiling. 
#41. SDJ. Strafe duck jump. Based on Strafe, Pre, #31, #40. Simple combination of Strafe jump and Duck jump.
#42. SBH. Stand-up bunny hop. Based on Strafe, #25, #26. Using fast jumping off at the time of releasing duck, you may not loose speed after jumping on high object and continue bhop in stand state.
#43. LadJ. Ladder jump. Based on Strafe, #2, #31, #32. Using increase of big speed while ladder climbing, you can take off over ladder for good height or direct speed to side and jump with strafes far from ladder.
#44. Ignore wall. Player's model is considered as wall which can be pierced with certain damage coefficient. If player is snuggling with wall, then game considers it as one wall with priority coef for player's model. Therefore, while hitting, only into player damage is counting. Also bullet will continue to fly further. But it doesn't work on walls which can not be pierced by your weapon. 

#45. Fake shot. All problem is in delay of information incoming to server. Animation and sound counts on client side immediately. But fact of shot can be counted only by server. 
#46. Player flashed beyond wall. Water in game is a texture like other, but allows to infiltrate into it. While appearing on border of textures, game will recount viewing of all models on map for this texture (water). And it's one moment, when moving up from water, displays walls and models simultaneously. But if models will appear at least for one frame before walls, we can notice it. 
#47. Climbing. Based on #4. Game allows player to climb on steep slopes. Speed of climbing depends on steep angle. But it's easier for game to push player to side as in surfing bug, so you should to take control of direction. Executing by move key directing straight to slope in stand state. 
#48. Clicking and stats. While fast-forwarding demo, it loads all moments of switching guns and calling stats up to this moment. 
#49. Player's belonging. While fast-forwarding and then rewinding, belonging of player will conform to moment before rewind. It's no matter where are these players existing after it. 
#50. Scope goes away. Similar to #49.
#51. Black shadows. While loading demo, sometimes, some sprites (images) which has transparent areas, loads with black areas. Shadow is a sprite too. This bug is random. Reloading demo usually doesn't change anything. 
#52. Buymeny stolen. While actuating recording of POV demo, screen shifts to other mode and reload all HUDs for its recording. This is happening quickly, and we can notice it, for example, due to displaying money. It has animation of refreshing while changing of number. But it's no any changing in this case. Developers just didn't make similar script for buymenu.
#53. Better vision through smoke. Features of engine in smoke displaying. Game does not count the smoke out of the screen in order for not loading videocard by extra processes. But smoke has a feature to change transparency on border gradually. So we can see weaker smoke on its edges, especially on upper right corner of screen. 
#54. Look through smoke due to partner. Sprites (Images) in game often has transparent areas. Radio sign is one of it and game doesn't count a smoke beyond the sprites, regardless transparency. 
#55. Double shot AWP. Viewing shot can be double at the moment of fast zooming into cases of shot without scope and within. But in any case, only one bullet can exist. 
#56. Strange sound of shotgun. The problem is in script which reload the shotguns by one bullet. When clicking mouse button while without bullets, game creates a clicking sound and does not call starting of reloading if no ammo in supply. But in case of shotguns, game makes it always. If you hold mouse button without ammo, script actuates and resets continuously and very quickly. In turn, after every reseting, game makes clicking sound. 
#57. Push the player out the textures, Dust2x2. Based on #8. While presenting out the textures we can observe the enemy in some places and shoot him by wallbangs. In so doing, he will never see you. 
#58. Climbing out the textures, Dust2x2. Based on #57. Developers left an ability to climb ceiling without textures.  
#59. Shells are louder than shots. Developers attributed wrong parameters for different sounds.
#60. Muted scout. Maybe it was made specially , in order for increasing of effeciency of inefficient weapon. 
#61. Door is breaking us, Nuke. Based on #22. Player, while preventing opening door and pushing it back, can provoke getting stuck in door texture. In this case, door quickly moves to close state and gets stuck too. 
#62. Clinging corpse. When player die, camera directs to murderer. But sometimes, if the victim is quickly pressing LMB, then his camera cling to murderer. In this case, murderer will see a clinging corpse. 
#63. Door blocking, Nuke. Based on Strafe, Pre, #31. Executing quite efficient strafe jump at the time of closing door, we can jump on upper section of any door. For this, you need to jump from threshold of doors. In so doing, door is blocked, but if you will continue to press move keys, second door can open.