#1. Jumps for speed. Player has some more speed while jumping than while running. Despite of short-term stops after each jump, average speed in case of frequent jumps will be some more than in case of run. Also you can increase speed if you'll press both keys - forward and any side key during each jump. 
#2. To ceiling from comp. This bug works because player in the air firmly strive to stick to nearest horizontal texture and to stand onto it. If we have height between object and ceiling texture little fewer than player's height, then player will stick to the upper texture of object. So, model of player will little appear in ceiling. Consequently, next jump will force player to stick to another higher texture, for example next floor, roof or you can jump through wall. 
#3. Wall hole. In any game textures protected from direct infiltration. But some textures in this game not enough protected. So, we can find holes which allow you to infiltrate through texture. 
#4. Go away by container. Barbed wire in game - soft texture, which give resistance to moving, but allow to infiltrate in itself. Game allows to jump through this wire on fence. 
#5. Wall hole in Priboi's base over door. Similar to #3
#6. Train hole. Similar to #3
#7. Wall hole. Similar to #3
#8. Stairs hole. Similar to #3
#9. Riding truck. Based on #1. Truck starting to move when player crossing certain line on map. This line lies on whole map, crosses a road behind the truck for about 50 meters. If you want to get truck, you need go straight on the road, kill all who can prevent you, and after crossing line move by frequent jumps. When you will appear forward from truck, you'll have to jump carefully onto hood. The hood must appear under player's legs at the time of top point of jump. In any other case player will be dead. 
#10. Fence jumping. Game allow to jump on thin fences. For making it you need fast jump off after landing, without using side move keys. Fence continuously tries to move you to the side and throw. To prevent it you'll have to correct your direction by mouse. If the fence turns, you'll have to release forward key before turn, then fast correct direction (by mouse) at the time of landing and press forward + jump. This is difficult but possible.  
##11-24. (secrets)
#25. Trigger of stairs. Trigger works in certain distance from stairs forward and backward. There is no dependence from impediments which on this distance. 
#26. Jump into roof and under floor. Similar to #3
#27. (secret)
#28. Riding helicopter. Based on #2. Unlike IGI 2, Flying helicopter is not stable texture, so player can not keep it for a long time. 
#29. From lamp to ceiling and basement. Similar to #2.
#30. Tower jump. Based on #2, #4. While falling player is gaining a huge speed. If you touch a barbed wire in air, then it, like a soft texture, will serve as bridge between air and solid texture (fence) by decreasing player's speed without injury. But it works not in any case.  
#31. Jump from roof into roof. Similar to #3
#32. Using enemy against gates. If you attract enemy beyond closed gates, then he can run to you. Gates in game automatically opens in case of enemy approaching. So, you can use it as infiltration to some places by ways that developer didn't guess. This is working in IGI 2 same
#33. (secret)
#34. Fence - roof - edge. Similar to #10. 
#35. Wire - roof - edge. Based on #10. While player on wire, he can jump off. In so doing if the fence will be under player, he will appear on it and can  go above fence. 
#36. Tunnel hole. Similar to #3
#37. From comp to wall. Similar to #2.
#38. Hangar - into wall. Similar to #2.
#39. Shoot the containers. Breakable objects have certain health. Developers left the ability to decrease it by any gun, not only bombs, as a mistake. They tried to make amends by attributing very huge level of health, thought that I will not get it.
#40. (secret)
#41. Jump into chopper, strange dude. Based on #2. Developers added enemy in this chopper but forgot add a scenario for him. So he can't even aim to player. 
#42. Explode the limousine. Thing that limousine can be exploded and mission fail, is normally of course. But limousine simply disappears and it's a bug.
#43. (secret)
#44. (secret)
#45. (secret)
#46. Jump through gates. Based on #1. Jump with pressing two keys has more speed and consequently more length. If you make this jump from edge of truck, you can get a roof of booth. Then you can easily jump through gates.
#47. (secret)
#48. Jump into canopy of door and inside. Based on #2. This bug works randomly and very rarely. 
#49. From radar by wall hole. Based on #3. Here you need to touch very edge of left wall and ceiling. There is very thin gap in these textures.
#50. Ceiling jump and megajump. Based on #1, #2. While running on top texture of catacomb ceiling, we must take to account that it disappears at the end. We should navigate by corridor left side, which is visible. We have to approach crossing of visible and invisible corridors. Then using bug #1 we should make boost jump to far low texture with keeping direction by side key and mouse. We have to fall into right edge of lower corridor. If we'll touch the ceiling of this part of corridor, then we'll lose speed without injury. 
#51. Vault - ceiling - Priboi's room. Similar to #2.
#52. From lamp to ceiling. Similar to #2.
#53. Trigger mistake. For some reason developers left two triggers different kinds on gates. 
#54. Alarm lamp throws into ceiling. Similar to #2.
#55. Megaphone in air. Mistake of drawing
#56. Hole under the door in office. Similar to #3
#57. For garbage can to roof. Similar to #2.
#58. From truck into ceiling. Similar to #2.
#59. Building - wall hole. Similar to #3
#60. On the edge of bridge. Game allows move on the edge.
#61. How to kill Priboi. Developers attributed Priboi the immunity from player's bullets but forgot about grenades.
#62. Evasion from bullets. If enemy stand close, he is shooting enough exactly to top part of player's model. If you'll aim to certain direction down, player will lean his head down. But enemy will continue shoot to same point. So all bullets will fly past. 
#63. Knife little throw. Animation of knife stab occurs some longer than real stab. If you stab 2 times and then, at certain moment, make same 3d time, further animation failure might occur.  
#64. Sniper gun kills in jump. Developers did not add dispersion for weapon while moving. 
#65. Shortcut by roof and fence. Based on #2, #3, #10
#66. Shortcut by lamp and fence. Similar to #2.
#67. From door to wall of tower. Based on #2. Similar to #3
#68. Lamp near tanks - to ceiling. Similar to #2.
#69. Tower hole. Similar to #3
#70. Over door to ceiling, megajump. Similar to #3
#71. From lamp to roof. Similar to #2.
#72. Hidden triggers. Many gates have hidden triggers which works not for player. But you can get it from sitting state.
#73. What are these triggers? Triggers are attached to certain coordinates on map but not to train. And even if train did not arrive, you can get it.
#74. Shoot the air defense. Similar to #39.
#75. Go through the fence. Fences in game are enough protected textures - there are no holes. But there is one place in game where fences cross by acute angle. If we'll go to zone between these fences and press forward and alternately jump, sit, then we'll can go through fence. 
#76. Grenade into abyss. Based on #3. There are some holes in textures that does not allow to go through but allows to throw grenade into it. In so doing grenade falls far from the textures. 
#77. Elevator got stuck. If we actuate the elevator before complete closing doors, then elevator get stuck in state that it not be able to start moving. In so doing, doors seems are opened but in program it's closed. If we press button one more time, elevator working will restore. 
#78. Wall hole in door, to roof. Based on #2, #3
#79. (secret)
#80. Priboi - wizard. Based on #72. Priboi is moving by certainly programmed trajectory, and no matter what can meet he on his way.
#81. Door throws into the textures. Based on #2. if you press forward and jump at the moment of start opening door by key, then wrong speed parameters will be attributed to player while opening. Eventually you can be thrown to the texture or beyond the door. 
#82. How to open door far from it. Based on #81. This one may occur if you press side or backward move key instead forward while execution of bug 81.