The arcade-style game Bombing Bastards hit Android TV last year, but now it's finally available on regular Android devices. This is actually a separate listing from the Android TV game, and it's completely free. Yes, like the real kind of free, not free-to-play.
If you've ever played Bomberman or a similar game, you'll get the gist of Bombing Bastards. You have to take out all the enemy critters without blowing yourself up, all the while grabbing power ups that make you more dangerous to yourself and others. This version of the game is single-player only with 30 levels and some boss battles. The controls have also been optimized for touch devices.
As for being free, it really is. There are no in-app purchases, but there are ads. When you die, you have the option of watching a short video ad to revive yourself. If you prefer not, you can just start the level over. Seems fair.