Air Zonk and Bonk's Revenge are the two best IMO. Blazing Lazers, Dungeon Explorer, Devil's Crush, Alien Crush, Bonk's Adventure, Bonk 3, Ninja Spirit, Legendary Axe 1&2 (moreso 2), and New Adventure Island are also great. And there's more I'm not thinking of right now, and I'm not counting CD or import games.
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[NO BARKLEY NO PEACE]