The Cheetahmen theme (from Action 52). The game may have been horrible, but the one music track (when it actually works properly) is actually rather catchy. There's a nice orchestral version on YouTube.
Crazy Bus title theme, but only a little, because it sounds *awful*. (Somebody in the aleatoric music thread mentioned this game.) Somebody actually made a 10 hour video of this random garbage; I don't think anybody capable of hearing would be able to sit through that video with the sound on.
Metroid 2 music. Some of the later tracks do something interesting; instead of having the whole track repeat after a certain length of time, different sound channels repeat after different lengths of time, creating an interesting effect. (See "Omega Metroid Territory", "Metroid Nest", and (I believe) "Metroid Hatchling".
Also, for something more conventional, The Elder Scrolls: Arena has some nice music. I particularly like the rain theme, the winter theme, and the theme that plays when you break into a house.