It's like Jaws 3! With zombies! But, sadly, no Louis Gossett, Jr. Oh well. This mod for Valve's Left 4 Dead takes the regular old game and renders the whole thing in 3D.
Proper 3D. Like, you need the red & blue glasses and everything. I'd imagine that makes the game 2x as terrifying, and as such, too terrifying for me, but for more adventurous souls, you can find details below on how to get it running, along with the minimum specs you'll need to do so.