Just play, don't pay!
There are a lot of games for Android, but only a few of them are NOT marked as 'ads', 'paid content' or just 'paid'.
So I've collected most of the best of 'money-free' games, see categories above or below. (4+ stars, 1000+ votes)
Enjoy :)
No category, Action, Adventure, Arcade,
Board, Card, Casual, Educational, Music,