I lament the fact that sending Christmas cards is a lost social construct...not that I, myself, am doing anything to help keep it alive. Still, I definitely appreciate the cards I get from diehards (such as my gramma, who has always puts my name in quotes- "Stacie"- as if it's a nickname) and I think we can all pretty much agree that receiving a "MERRY XmAS!!!" text message just ain't the same as receiving an overpriced piece of cardboard with a handwritten message in it.
Here are a few video game-flavored holiday selections, some of which you can even purchase. Maybe next year I'll make an effort...yes, next year...
This Fallout themed card is courtesy of Bethesda Softworks; 1up.com has this and other cards sent out by development companies posted here.
Oh, Left4Dead, how I heart thee! Though I always play as Zooey, I love the three guys just as much. How can you not? Francis hates everything, Bill is decidedly Colonel Tigh-esque, and Louis is always "grabbin' peels". You can get this card and plenty more (as well as a selection from L4D2) at The Valve Store.
Also at The Valve Store is this Portal/Aperture Laboratories card. Ah, my faithful companion cube. I done euthanized it.
Finally, BioWare posted this Mass Effect 2 card at their blog. Mordin is so damn cute, my coal-black heart grew three sizes just looking at him! Then my heart exploded, because it being three sizes bigger is not actually a good thing.