Xbox live is currently running an ultimate game sale where they have new deals everyday(for one day only) and also deals that will last the entirety of the full sale.
Day 1 Sales(now expired)
Halo 3 $9.99 67% off
Halo 4 $39.99 33% off
Halo Reach $9.99 67% off
Halo Wars $9.99 67% off
Day 2 Sales(now expired)
Assassin's Creed Brotherhood $9.99 50% off
Assassin's Creed Revelations $14.99 50% off
Assassin's Creed II $9.99 50% off
Assassin's Creed $9.99 50% off
Day 3 Sales(now expired)
Resident Evil: Code Veronica $4.99 75% off
Resident Evil: Operation Racoon City $19.99 50% off
Resident Evil 4 $9.99 50% off
Resident Evil 5 $9.99 50% off
Resident Evil 6 $19.99 50% off
Day 4 Sales(now expired)
Call of Duty: World At War $9.99 50% off
Call of Duty: Black Ops $19.99 60% off
Call of Duty: Black Ops 2 $49.99 17% off
Call of Duty 2 $9.99 50% off
Call of Duty 3 $9.99 50% off
Modern Warfare $9.99 50% off
Modern Warfare 2 $9.99 67% off
Modern Warfare 3 $29.99 50% off
Day 5 Sales
Batman: Arkham City $14.99 50% off
Borderlands $9.99 50% off
Borderlands 2 $29.99 50% off
Fable III $9.99 50% off
Dead Island $9.99 67% off
Fallout: New Vegas $9.99 50% off
Portal 2 $14.99 50% off
Red Dead Redemption $14.99 50% off
Dishonered $29.99 50% off
Persistent Sales February 26 thru March 4
Dirt 2 $4.99 83% off
Grid $4.99 83% off
Dark Messiah of Might And Magic $2.99 85% off
Rayman Raving Rabbits $2.99 85% off
TC Hawx $4.99 75% off
Rainbow Six: Vegas $4.99 75% off
Kane & Lynch: Dead man $4.99 75% off
Call of Juarez $4.99 75% off
Tomb Raider Legend $4.99 83% off
TC Ghost Recon Advanced Warfighter $4.99 75% off
TC Ghost Recon Advanced Warfighter 2 $4.99 75% off
Virtual Fighter 5 $4.99 75% off
Bioshock $4.99 75% off
El Shaddai Ascension of The Metatron $2.99 85% off
The Darkness $4.99 75% off
Theres alot of good deals in there and I just grabbed RE: Code Veronica since that price most likely won't ever be lower than that. I will try and keep up with updating the deals daily but they can also been seen directly from the XBL dashboard.