Tons of stuff:
I have ~135 game apps plus some that are not exactly games but not exactly for productivity.
I have lemuroid and a pile of old console games.
I have a few sites for doing other little games, like daily Akari.
highlights:
Collapsus
Endless Sky
Pixel Dungeon
Luanti
Gladiabots
Mindustry
PartyHardGO
OpenTTD
Oxenfree
Revoltaire
The full set of games by Yiotro (a dev who puts it all out there for free, no ads, and lets you buy in if you like it)
Terraria
Underhand
Space Chem
A collection of puzzle games off of Fdroid just called puzzles. It has akari, sudoku, minesweeper, signpost, galaxies, towers, etc. All the games you might find buried in the back of a newspaper.
Stardew Valley
Tic-80
A pile of games from itch.io
You wish it looked that cool.