Recently I discovered that people have actually started working on Mushroom Kingdom Fusion again, after it was in hiatus for a long time. It used to be maybe my favourite fangame ever, combining all kinds of different franchises while still keeping the Super Mario Bros 3 / Super Mario World style gameplay.
The game still isn't finished but I'm surprised they're working on it at all.
Levels included in this video:
00:00 Intro
00:21 9-S2 Anciena Pyramid (Secret Exit)
07:10 9-5 Silius (Troop of Cannons boss fight)
16:01 9-7 Infested Station (Red Falcon Flood Beast boss fight)
26:56 Super Metroid Battle #3
28:42 9-S4 Wart's Nightmare
4