A horror-like game such as that HL2 mod, but expanded-
There are different "classes" of hunters and hunted.
For instance, the nearly invisible knife-wielding Hidden is a single class of hunter, with a few different choices- maybe a knife lunge, or alternatively, a skill that makes noise to distract the hunted.
Other classes include ones that can take advantage of map features- small aliens with the ability to crawl about in areas too tight for others, with stingers that can cause various things such as blindness or slowed movement, even poisons.
Humans get classes too- anywhere from the Soldier who has better weapons, to the Scientist who has equipment able to detect Hunters. Both sides have objectives- the Humans might try to set up monitoring equipment- the Hunters can sabotage it, however, but there are multiple locations.
The Humans can all group together and go after one spot, but it only takes one stealthy Hunter to sabotage their work.
The Humans can split up, but it makes them easier targets- they can possibly attempt to set up at multiple locations, and if just one is successful, they get their bonus.
When the time is up, if there's a functioning setup, the Hunters are revealed and they'll have a much harder time hiding. If there's no functioning setup, but one was sabotaged, the humans get many false positives and make it much harder to detect a Hunter coming. If there's no setup at all, no one wins.