Currently seeking funds on Kickstarter is Tetrapulse, a PC co-op shooter taking place on a planet where the scary robot aliens are many and the resources are few. Which is probably why the heroes are forced to use their own health as ammo.
Tetrapulse uses procedural generation for its levels, where the goal is to ferry along the Heartstone, a large rock used to revitalize the player characters, to the defence beacons strewn around the map. Activating the beacons generates a planetary defence shield which gets rid of the invading bug-like robot-aliens in that area.
Said aliens, of course, are constantly trying to stop you, which is where the "health as ammo" mechanic comes in. Players will have to think about each attack, rationing their health and timing their strikes so as not to accidentally off themselves while defending the Heartstone.
Its developers are asking for $US15,000 to put the finishing touches on Tetrapulse, with one of those finishing touches being online multiplayer -- fairly important for a co-op title. If you're interested, you can take a look at the project page here.