Check the Mac Appstore for free versions of:
-Minesweeper
-Solitaire
-Mah Jongg
-RailMaze
-Pawn'd (lite)
All free, all good.
Not free, but the best non-violent game I've played in YEARS has got to be Valve's Portal/Portal2. Presented as a shooter, but something much, much larger. You kill no one during the entire game, and the puzzles presented are mind-expanding treats. The story and atmosphere in Portal2 is better than any movie I've seen in the past decade.