Reply 60 of 81, by Kerr Avon
Shouldn't Spelunky and Cave Story be in this topic too? They are both apparently excellent games (I've not yet played either game), and they were originally released as freeware. The freeware versions of both games are still available, though if your prefer then you can purchase graphically enhanced (and maybe more feature-rich, I don't know?) versions, too.
Also, there are several free first person shooters listed here: