TWT_Zombies is alright, but they usually don't go for the bots, just you. And their pretty stupid.
What someone needs is to make a "Bug Hunt" mutie, similar to TWT_Zombies, but with the aliens from Aliens. With some smarter AI and making them faster, stronger and kill with one hit, oh, n wall run.
That would be awsome, great for some offline target practice!
Just you have to be able to turn off respawning aliens through an .ini or something.
Play a level like Chasm, on CO-OP with like 5 other players/bots, and just go around eradicating the aliens building by rbuilding, would be great on Frozen, except you'll have to convert it to TDM