It's mikeyk's Sledge Bro, and I made him nasty. He takes two stomps to kill, not just one, and the first stomp has a nice effect of throwing him backwards as he takes damage while flashing through the sprite palettes. Note that he can't be stomped a second time until the flashing finishes (preventing a cheap and easy win).
Secondly, setting the Extra Bit causes him to throw THREE HAMMERS AT ONCE, which spread out in a nifty triangle formation. Don't think you can hide inside the blind spot inside his arc anymore either-- you have to dodge BETWEEN the hammers, and since they fall at a diagonal angle you have to compensate for that too.
You can use this souped up sprite to wreak serious havoc for a hapless Mario fan when he reaches your level!
No Readme included and everything in the .ASM is organized and very neatly documented.