Grand Theft Auto II/YMMV

Acceptable Targets: Elvis impersonators. Whenever they appear, killing all of them will give you a bonus, as well as the announcer bellowing "Elvis has left the building!"
Anticlimax Boss: All of the bosses, once the player has completed all of the missions. They come without reinforcements despite not being especially strong in any way - thus, the final mission of each level is just to kill three random enemies as they come.
Ear Worm: Taxi Drivers must DIE!
Karma Houdini: The player character himself, especially if you're good at the game.
What an Idiot: Incredible stupidity among non-playable characters is incredibly rampant, whether by design or by programming limitations or both. Even aside from flat-out cases of Too Dumb to Live, there are forms of stupidity not directly lethal to oneself, such as a cop not considering it suspicious that you would be punching random civilians in front of him.