Invisigun Heroes is "a multiplayer, single-screen stealth battle arena game with a twist". That twist being that every single player -- even the one you're controlling -- is invisible on the screen. Which sounds like a nightmare! But while the player model is invisible, your effects on the game world aren't, so any time you (or another player) run into something, cross snow/dirt or go through water, you're alerting other players to your whereabouts.
Ditto for when you shoot, as your gun lights you up for a second. Which means that the game looks like a constant struggle between risk and reward, as to get anything (like a power-up) or kill anyone you need to move and shoot, but in doing so you leave yourself open to attack.
You can see all this in action in this (excellent) trailer.
Invisigun Heroes is looking for a very modest $US32,000 on Kickstarter, with an initial release on PC/Mac/Linux followed by consoles (if it hits stretch goals).