We don't see too many 3D pony fangames, but Oddwarg (the man behind Corruption, overall winner of the 2012 My Little Game Jam) has decided to release the trailer for a game he's been working on a week before he sets off to sail the sea in his yellow submarine, which is apparently his idea of a vacation. Aside from Rainbow Dash's nice animations the game looks pretty bland, but since the code is apparently lying around somewhere on the internet somebody could probably fix it up while Oddwarg mucks about in the sea of green.
As to what platforms the game runs on...I have no idea. Oddwarg didn't specify where on the internet he keeps the source code (although I suspect that it's probably on GitHub), but he did say that it was released under the MIT license which means that you're free to modify the game yourself and port it without asking him. In my humble opinion fangames would be much safer from Cease & Desist notifications if they were all open source, but apparently some folks really don't like it when others can read their messy code...