I love exposing bugs in games.
I was playing c2a5, and having a pistol fight with the ickyosaur, when I killed it mid-leap. It hung in the air, twitched, and rolled over, just like when you kill it in the water. Then it slowly floated down towards the water's surface.
"Hey look! A floating prehistoric fish! Fasinating!"
"Sure, doc, sure. Someone's had one to many aliens appear in front of him"
Hilarious.
Side note, press F5. I got a new avatar, to celebrate my re-discovery of the fun of my gamecube games.
And nice glitch find
EDIT: There. Press F5 if you don't see it.
off the top of my head, I know deus ex is one of those. Fallout 3 is another.