[PC, Linux, Mac, Steam] Free: Caveman World: Mountains of Unga Boonga (Was $2.99) @ Steam

Caveman World: Mountains of Unga Boonga is a retro inspired platformer adventure game set in fantasy prehistoric time. You play as a Caveman, exploring various levels and overcoming physical obstacles. Levels become increasingly more difficult as you encounter enemies, obstacles, traps and more!

422 mostly positive reviews.

Credit to Hiphopopotamus at OzBargain