Limiting myself to one track per game, here are some of my favorites:
Morphogenetic Sorrow (9 Hours, 9 Persons, 9 Doors)
Discussion-HEAT UP-8bit (Danganronpa 2)
Karma (Ever17)
All Or None-Piano-
Thanks For Being Born (Umineko no Naku Koro Ni)
Blue Bird Lamentation (Virtue's Last Reward)
Interaction (YU-NO)