Volition thought up a nice way to give something to Red Faction: Guerilla fans for Christmas, while at the same time bringing some new players into the game. Running from December 17th to the 21st, there will be a "Get Your Ass Back to Mars" event running. If you were looking at a good time to build some XP next week will be a good time, as everyone playing will get a x5 XP bonus for the five days the event is running, in every game mode.
If you have the game and perhaps put it aside for a bit, you might want to get back into it to unlock stuff like the Ostrich Hammer (which I assume has more to do with kicking ass then it does ostriches).
Also for further festive gift-giving, on the RedFaction Twitter page they'll be giving away DLC unlock codes, during the event. Unfortunately, all this good stuff is only for the console versions of the game. PC gamers get the 'ole Christmas shaft this time around.