Planescape Torment - "Deionarra's Theme"
-> one of the greates rpgs EVER

http://www.youtube.com/watch?v=OZOuy4YM0AI

Mirror's Edge - "Puzzle Theme"
-> cool gameplay, great soundtrack, but no story

http://www.youtube.com/watch?v=TbdBNMTR8mM

Diablo II - "Harem"
-> great game - the definition of addiction

http://www.youtube.com/watch?v=fDtWBTwIL8Y

Crayon Physics - "Ghost - Lullaby"
-> never played, but one of the best pieces of music out there !

http://www.youtube.com/watch?v=acEYrld-9sQ

Scott Pilgrim Vs. The World: The Game - "Anamanaguchi - Another Winter"
-> never played but this song is great!

http://www.youtube.com/watch?v=wduS15Bv-Bg