I like Trigun's soundtrack. Good ol' fashioned electric guitar that hits you straight to the soul mixing in with the sweet sounds of the fluttering flute that makes you feel like you're fluttering on air. Can't go wrong with that.
Nujabes makes real good beats in the Samurai Champloo soundtrack, though the melodies tend to get repetitive real quick. Though I'll openly admit that there are beats on that song where you just sit back and listen, and head noddery just comes at an instant.
Cowboy Bebop's good too, but I haven't really checked it out, and One Piece is good as well, since I like it when the character soundtracks actually show off Luffy's singing talents, if he even has any. :luffy