To Zerokk: I totally agree with you on both those points, dude. Besides, Sniper Joe as a Robot Master? If that were the case, then we might as well call Sniper Joes "Joe Men" or something along the lines of that.
Anywho, here's a Robot Master I just made recently, named Raccoon Man (or Tanuki Man, whatever floats my boat), based off the Tanuki from Japanese folklore.
(OMG, I got so much Robot Master ideas in my head, not even I can keep track of 'em!

)

Name: Raccoon Man (or Tanuki Man, as in the Japanese folklore creature which is a raccoon trickster, capable of transforming into anything and anyone)
Weapon: Stone Defender (Shield weapon, stones can be shot at foes one at a time, summoning shield uses up 4 points of Weapon Energy)
Description: A raccoon-like robot capable of transforming into anyone and summoning stones to use as a barrier, he gets weakened if the leaf on his head is removed.
Good point: Joyous
Bad point: Mischevious, gullible
Likes: Sake, playing tricks on others
Dislikes: Being tricked back
Quote: "Me? Copying you? I don't know what you're talking about."
Ideal stage: His stage could take place outside of a Japanese shrine with enemies that pop up out of nowhere, enemies that look like items (just to fool naive players, muhahahaha) and (le gasp) Yoku Block puzzles. Eventually, when you're inside of the Japanese shrine itself, the trickery only increases until you eventually get to Raccoon/Tanuki Man himself. This stage would require players to memorize the enemy patterns and the Yoku Block patterns along the way, as well as keep players on their toes for any tricks up ahead that could either be used to their advantage or their downfall.