Soo many good ones..... I tried to chop down my favourites list a bit but I still have quite a few.
Donkey Kong Country: Fear Factory, Jungle Groove.
Donkey Kong Country 2: Hot Head Bop, Kannon's Claim, Welcome to Crocodile Isle, Swanky Swing, Krook's March.
Donkey Kong Country 3: Rockface Rumble, Nuts and Bolts.
Donkey Kong 64: Frantic Factory, Gloomy Galleon, Creepy Castle, Hideout Helm, Crystal Caves.
Banjo-Kazooie: Rusty Bucket Bay, Mad Monster Mansion, Treasure Trove Cove, Gruntilda's Lair, Final Battle.
Banjo-Tooie: Grunty Industries, Cauldron Keep.
Huh.... I seem to have quite a taste for factory themes. Hahaha!