There was one time I was playing STALKER: SoC, modded, and I had a sniper rifle. I was in the starting villiage when the military decides to attack. I marched up to one, shot him in the head from a meter away, and watched him ragdoll-launch himself through a fence, and a wall. Then get stuck partway inside a wall of a nearby house.
Also, there was one time I saw some NPC crouching, shooting the ground at the bottom of a hill. I thought he was trying to shoot someone on the other side of the hill. He then stood up, and kept shooting that same spot.
As for unintentionally funny: in the intro, the voice acting is so...well, enthusiastic...just watch: http://www.youtube.com/watch?v=EMvMtEnXoMM