The Steam holiday sales are probably easier on my wallet than other people; to start with, I'm restricted to games that release on OSX, and furthermore set my price cap at around $5. So despite the multitude of offerings, it's rare that I see something that fits both my criteria.
However, one that did recently was VVVVVV, which was on sale for the incredibly low price of $2.50. The reviews were all positive, and although I wavered for a bit, there wasn't a downside to a game for that cheap, and after briefly playing the demo I semi-impulsively purchased the game.
