Qwak
(Team 17, 1993, Amiga)
This little gem is included in the new A500 Mini system, and I really recommend getting a friend and a second controller for the best experience.
Think bubble bobble, platforms, a single screen, multiple enemies. Now throw in 2 adorable ducks as playable characters, a simple objective (get the keys, open the door, get to the exit) and a myriad of different game modifiers and powerups to keep you on your webbed feet. 80 levels, a great soundtrack, and the difficulty ranges from "Easy AF" to "OH MY GOD"
Boss battles, fruit, spikes, potions, gems and a lot of swearing. On the mini, the original hardware or WinUAE.... GO PLAY QWAK!