Free stuff in two sentences.

Punch Quest [iOS] Punching, questing, punching, getting sweet new loot and punching some more. It's a simple idea executed well but there are some setbacks, hitting lock-screen destroys your game, saves sometimes go missing and there is an ominous update coming out to help monetise the game 8/10.

Train Conductor [iOS, Android] It's free and if you really want some train directing action it isn't bad. Honestly I get bored of the concept very quickly 5/10.

Weird But True [iOS] Packed with so many facts you could remember them all after one viewing. You know what is really weird but true about this app, you used to have to pay $2 for it 3/10.