Left 4 Dead (my brother's getting 2 for Christmas).
There is nothing more rewarding when you leap onto an unsuspecting survivor and pull their nipples off, and it excites me in ways I should probably tell my therapist about.
Also, epic instant kill spots with smokers that leave survivors wonderng "should I just kill him and end it for my partner, or go on ahead, knowing that her fate has already been sealed?" just fill me with pride.
And of course, falling from 50 feet and using your explosion to cover all 4 survivors in "stuff" is definitely good for a "knee-slapping" laugh.
As is using the Incredible Hulk to knock survivors off of a building into their deaths 2000 feet bellow.
My favorite thing is that when I play as a human, I know that I'm good at the game because
A) My Infected and Special Infected number of kills are usually double that of 2nd and 3rd Players,
B)Whenever I die, my team mates usually don't last much longer after that. Maybe a minute or 2,
and C) (probaly because of A an B) My partners instictively come back to save me whenever I get attacked and seperated.
That just adds icing to the cake.