So, I recently got a mac... and I wanted to pick up a cheap time-waster game from Steam. I settled on Dungeons of Dredmor, from Gaslamp Games. I have to say, it was money well spent (only $4.99). It's a hack and slash dungeon crawler with humorous content, pretty much a send up of the genre. In my short time playing I've picked up on Diablo II, Indiana Jones, Starcraft, LOTR, and A Song of Fire and Ice references.
The gameplay reminds me of Nethack, but with better graphics and a more light-hearted storyline. You can die pretty randomly, but the characters are pretty much a throw-away each time you play. You do have a save feature, but the notice on the screen "Congratulations, You Died" each time you bite it should be an indication of the gameplay style. It really satisfies my loot-lust born from Diablo, and it has a skill and crafting tree to boot.
All in all if you're looking for a solid hack/slash dungeon crawler to waste some time on, you'd do well with Dungeons of Dredmor. Now if you'll excuse me, my bloodmage archaeologist viking vampire has some killing to do.