Ever wanted to play the classic Super Mario Bros. with a Portal gun? No? Oh well, some guy is making it.

Mari0 is a game being developed by the small two-man indie company Stabyourself. The gameplay is simple really, Super Mario, with portals. Like throwing hammers back at Hammer Bros? You can do it.
Another thing is, this game is being developed with Multiplayer in mind, so you can have up to four people total. Currently there is a splitscreen option that makes traversing the levels much easier and less annoying.
http://stabyourself.net/mari0/