Enough Plumbers, by Radix and MrPodunkian is a well-crafted puzzle platformer with a cloning mechanic and character transformation power-ups. The action is secondary to the puzzle element, although there is some base level of dexterity required.
I thought the polish was very well done, particularly the music (although the Mario-like sounds every time you collect a coin do get a bit annoying after a while). The puzzles are also very clever; most of the puzzles later on require using several of the the different clones in different ways.
My only real complaint is that up is jump; I prefer some other keyboard button alternative, so that I can move with one hand and jump with the other. But because the game isn’t that action-based it wasn’t as big of a problem as it’d be otherwise.
The game is based on an earlier game of Radix’s called Enough Marios, which is simpler and less polished, and which I link to mainly because of its awesome cover art.