I bought "Stubbs the Zombie" this weekend, Steam's selling it for 75% off (
Steam News) - I would've posted sooner, but I thought I should play the game before suggesting it, and it took literally all weekend to download on my crappy connection.
It's like a simplified version of the GTA - no weapons or missions - you run around eating people's brains, and converting them into zombies. You can also possess people and stuff. All in all pretty cool - has a "arcade" feel to it - it's challenging, without being frustrating or too difficult.
So if you've got $5 to spare, it's worth buying...