A Survival of the Minions style map.
I've seen alot of survive the Zombies maps. Same goes for survive <insert ridiculously OP creature(s)>. I haven't come across any survival type maps where you're tryign to survive hordes upon hordes of little creatures.
So, how about this:
Inheritance (A twist on the whole "the meek shall inherit the earth" thing)
Goal: To survive for as long as you can against increasing numbers of minions (There's no win condition, the idea is that the player must live as long as possible)
Minions: Spiders, Rats, Arachnathids, Mud Golems, small custom models with attack animations from THW, etc...
As for the type of survival, there are two:
1) Hero only
2) Base (army)
If you want, you could put a vote system in place for players to choose which mode in-game. Hero only would rely on items and excessive hiding, while Bases would be more focused on maintaining defensive positions.
Again, there is no "last wave" to survive. If you've played Bejeweled 2 Action mode you'll have an idea as to what I'm talking about.
//\\oo//\\