Braid and N+ if you like platformers, and you don't need a gold account to download the games. It comes with a Silver (free account) and I believe you get one month of free gold service just for activating. After that expires you will not be able to play multiplayer. SP still rocks in those games.
Edit: BTW I see the pic of your setup. That looks nice!!! My wife would have a fit, but enjoy it while you can.
(Deep down I am jelous, I am still rockin the CRT <SDTV>)