There's three different ratings for replays, one of which is "humor." That said, if you find things like this to be Bloody Hilarious, there are endless possibilities for laughs. Also, someone with that sense of humor will be laughing the whole day when they first find out about the game.
This Troper once was playing a custom map as the Irresponsible Dad, all was going well until he got decapitated and his head was just barely hanging on by the spinal cord...then things went south when the head got stuck in the bicycle wheel and kept going until the carcass eventually fell face forward and got crushed by the moving bicycle wheels. Oh, and this was all while the child was still alive. And watching.
I was once playing the map Car Thief and I grabbed onto my car (The thief was in it) which flipped the car over, decapitating him. I stayed on the ground a little bit. All of the sudden, the car thief ran over me while decapitated.
On certain stair-based levels, if the character's body is cut in half, but is still connected by the intestines, you can get a bizarrely morbid and hilarious slinky effect.
On the level, "harpoon catch", you use a harpoon to stab an old man, before falling onto the finish line. When this troper fell onto the finish line, his entire body just split into bit, while the old man was completely okay. What did he say? "Ow, mah leg."
This troper remembers an instance playing a rather high-quality Zombie Apocalypse map where you "used" a shotgun to kill some zombies in a scripted sequence. I somehow managed to jump in such a way that I was firing a shotgun with Segway Guy's teeth. Appropriately, my run through the level ended when I ran into the last zombie. I somehow managed to blow my own head off and watched as the headless corpse rolled onto the elevator that acted as the level's finishing point.
Due to the way the Pogostick Man's physics works, he can achieve some of the most precise locomotion in the game by just slamming his face into the ground and "cartwheel" forward or backward.