Depends on how much effort are you willing to invest on it.
From 2d metriodvania to simple building-crafting game to endless 3d zombie shooter games. There's gameplay and story of the game you should think about too. One is nothing without the other.
You can try seeing any recent game jams or indie games and try getting any inspirations or ideas from 'em. They're a nice source of seeing how they do stuff which are great. Though its best to try having some of your own too.
Since you're interesting for a funky funsie, try one of those endless runner games, or cozy farmer/tycoon cookie clicker game, or like that one mobile game called Soul Knight, random dungeon game with characters with different classes and abilities.
In the end you're your own author and developer who can put anything and everything, good luck with it. But, make sure you have fun whilst at it.