And before you say Left 4 Dead, Killing Floor, and World War Z, that's not what I mean.
I'm talking about round-based, endless zombie shooters with an emphasis on killing zombies for points that you can use to buy perks, unlock doors, upgrade weapons, and use traps. From what I've searched, even on Steam, I can't find anything like it. You'd think indie games would want to milk this for all it's worth.