Wal-mart, mainly because every time I went there, the people were not helpful in the least, and nobody was staffed in the electronics department of the store.
All you have to do is guess a number 1-100 (I will pick 2 random numbers) and say what you want. The Mass Effect 2 code is for Xbox 360 and the Medal of Honor code is for PS3.
My top ten would probably be:
1. Shadow of the Colossus
2. God of War 2
3. Metal Gear Solid 3
4. Final Fantasy XII
5. Disgaea 2
6. Ratchet & Clank Up Your Arsenal
7. Twisted Metal Black
8. Gran Turismo 4
9. Soul Calibur 3
10. Kingdom Hearts