What's a good stress relief game?

I'm looking for a good game that has one or both of the following aspects: Either A: Lots and lots of killing without a whole lot of story line and plot. Think Dynasty Warriors. Or B: Something that allows for tons of creativity. Spore's alright, but not quite enough. I've got a pretty amazing PC, and as best I can tell, it can play any game currently on the market. But that is the only game system I have. The person who suggests the game that is the most fun for me wins best answer.