God Hand (PS2)
You can literally spank your opponents in this fighting game that looks like Dead or Alive Meets the Wild West. While it's not the first time that spanking something has been associated with video games, it's probably the most satisfying.
Lego Star Wars II -- The Original Trilogy (Xbox 360, Xbox, PS2, Nintendo DS, GameCube, Game Boy Advance, PC, your toaster)
This looked like it would be a forgettable sequel, but it's about the most legal fun you can have while playing a video game. Plus, who hasn't gone back through the game and just smashed everything in sight?
Mission in Snowdriftland (your web browser)
It's simple, it's fun, and it's free. The perfect game trifecta. Whenever you're looking to kill a few minutes with some gaming, fire this one up and clear a few levels. You are guaranteed a good time or double your money back.
Nancy Drew: Death by Design (PC)
Nancy's 14th, that's right folks, she's got 14 under her belt, video game teaches you not to mess with anyone in the fashion world. Nancy Drew is one tough girl, and trust me ... you don't want to get on her bad side.
See also: Joystiq's Game of the Year