The people at Sprites INC. ripped some sprites from the Megaman series and found some nice unused stuff in there! Some of the most interesting ones are:
Megaman 9 Skateboard enemy falling sprite:
Megaman ZX – DS debug room:
Megaman 2 unused tiles:
Megaman 7 unused enemies / sprites:
Megaman Power Battles & Fighter unused prites:
Megaman Battle Network 1-6 unused sprites:
You can find more Megaman unused sprites in the Sprites INC archive!