What cool games are unique to OS X?

I recently purchased an old G3/450 running OS X 10.3 from a friend, and
I was wondering what cool and unique games are out there.  I'm
completely new to Macs and OS X myself, so I don't really know where to
start.

I like light-hearted action games with simple controls (well done
remakes of arcade games, side-scrollers, etc), CRPG games, and really
most anything except bloody 3D games and most card and puzzle games.

Thanks in advance for any recommendations!


-- 
Karl Garrison