Nothing says Christmas like a Mecha Engineer Update. Now those evil robot bastards have an engineer that can do all the stuff you hate about human engineers. Have fun dealing with robotic teleporters and sentries among the onslaught. We get to enjoy the madness on a new map called Big Rock too.
Valve added a bunch of winter themed Swissmas hats, accessories and festive weapons to add some holiday cheer to your death and carnage. Check out this link for the full list: