I beat Kirby Star Allies earlier this week. It was fun, though the action could get pretty cluttered.
There's also another Doom 1 megawad built to that concept called Wonderful Doom which is equally worth playing.Yesterday I finished a Doom 1 megawad called Doom the Way id Did. Its a total replacement for the original 3 episodes of Doom, done intentionally aping the styles of John Romero, Tom Hall, and Sandy Peterson. It was amazingly good and quite difficult at times.