Just plain fun.
I mean, who doesn't like viscious beheadings, blood and gore, and various weapons of torture?
Keeps me entertained for hours.
It's also kinda interesting to see if you can get your bear/kitty/whatever thing to the floor with as little damage as possible. Sure its not as much fun as smashing them up, but it adds a little bit of challenge.
Also, have you considered a level builder option? I'm sure that everyone would LOVE that feature. Some other ideas: more hitpoints, more characters, and more devices of painbringing. ';,,,;' (<-- devil/monster thingy)
PS: level 9 is my favorite! XP