http://stabyourself.net/mari0
Can download it for Windows, Mac and Linux.
From the site:
"Two genre defining games from completely different eras: Nintendo's Super Mario Bros. and Valve's Portal. These two games managed to give Platformers and First-Person Puzzle Games a solid place in the video game world. But what if Nintendo teamed up with Valve and recreated the famous Mario game with Portal gun mechanics?"

Played for 5 min. last night. Couldn't imaging running the whole game with that control scheme. Very interesting though.