Best $20 Game on 360?

So recently, for an unspecified celebratory event, my friend gave me a card for 1600 Microsoft points ($20). I was wondering what you guys think is the best Xbox 360 game for $20 or less. Some good ones include:

-GTA 4
-Mirror's Edge
-Just Cause 2
-Assassin's Creed (2, Brotherhood, or Revelations)
-Some EA Sports game
-Halo 3
-Left 2 Dead 2

What other good games are there?

For $20 or under some of my favorite are:

Shooters/RPG
Fallout 3
Fallout New Vegas
Borderlands
Borderlands 2

Action/Shooter
Red Dead Redemption
L.A. Noire

Action/Adventure
Batman Arkham Asylum
Batman Arkham City (GOTY)

Shooters
Call of Duty: MW 2 or 3
Gears of War 1,2,3 (I would play them in order)
Bulletstorm
Singularity

RPG
Final Fantasy XIII
Final Fantasy XIII-2
Dragon Age Origins Bundle
Blue Dragon

There's a lot of great games that you can get for under $20! Those are just a few of my personal favorites. :]

Fallout 3 or Fallout New Vegas. I don't know about on XBL, but at a game store I saw Fallout 3 GOTY for $9 and I bought New Vegas with all DLC brand new for $20.

Mirror's Edge or GTA 4 are both good choices.

Forget best 20$ game, Halo 3 is the best game in the system.
Rayman Origins is really freaking good too.

However, since Halo 3 is free right now to all Live Gold members, go with Rayman Origins.