The Donkey Kong Country series soundtrack as a whole is great, especially the first two, 64 and Tropical Freeze. I've got a lot of respect for David Wise (and Grant for 64, among other things) as a composer, I don't often see a soundtrack that pulls off some of the beautifully chilling, calming, and jazzy ambient vibes that Wise is known for.
It's not one that I really go back to, but Halo Reach's OST really stood out to me and I think it deserves a mention too.