As a general rule of thumb, if you can't think of your own GENERAL AND EXTREMELY BROAD ideas for a game, you're not cut out for making a game.
And by general and extremely broad, I mean: Fighting, Role-Playing, Survival, etc.
I have one you can make a giant house with zombies then once they get outside there are a lot of slender man so they have two choices kill a lot of slender or a lot of zombies and there's a box inside and outside but they have to shoot there way there