Since I need to do some recommendation for the holiday event I figured I'd at least recommend something that not everybody owns already.

Eets is a fun little puzzle platformer vaguely like lemmings and the incredible machine. This little bunny thing will walk back and forth interacting with objects in whatever way. Some of these adjust his mood, a scared Eets will be too afraid to jump over gaps, while an angry Eets will jump a mile.

You place various elements like cannons and cookie launchers and whatever else to get Eets to the goal, often involving you firing cookies to make him happy, or other mood changing items.

It's a fun puzzle game that gets pretty difficult.

Also when angry Eets rawrs it is adorable :3

This game is easily one of the best values on Steam. It's a bit difficult the first few times you play but soon you'll be much more capable. There's a ton of replay value. It is a bit demanding on your system since it's flash though, and also requires something like Joy2Key for joystick support which is essential. Sometimes I even play it instead of TF2...