What are the best couch/local co-op PC games?

D:OS2 has an expertly composed soundtrack, giving the world a great amount of color and atmosphere. From the mellow flute permeated with ambience and a divine chorus when you travel down a road, to the upbeat strumming of string instruments as you ransack a tavern, to even a ominous orchestra during a confrontation with a dragon. Wherever you are in the game, the soundtrack is a joy to listen to.