If you hadn't heard CROSSOUT, a new post-apocalyptic free to play MMO is in open beta right now. In this game you can craft your own unique battle vehicle from various parts you receive from previous PvP and PvE battles. It is fun to watch the chaos created as parts fly off your enemies when you hammer them with auto-cannon and shotgun fire.
I've only played a few hour of it and I'm having a blast (all puns intended).
Feel free to check it out at crossout.net/en