Super Mario through the Ages is my new favorite Mario 64 rom hack. Just about every world is a hit and the fun really never ends. The level design is great; Kaze has really taken a step up in that department. The theming is fantastically fun, and the Pokémon wrinkle is super interesting if not a bit under-utilized. I wish you were able to switch Pokémon anywhere so that they could be more aligned with the stars. I also wish the training rooms were a bit longer, but I still love those. The hub world is also very neat and I love how the island progresses as you gain more and more stars.
El Dorado, The Great Wall, Planet Namek, DK COLOSUS. There just so cool man.