MechWarrior Online is an upcoming F2P title.
It is currently in development/beta but apply and you'll probably get in. For instant access there are founder's packages available. Requires top of the line gaming rigs for smooth play with CryEngine 3.
I got a mercenary corp unit going if anyone wants to join me. We're mostly North America based and play around 8pm-1am EST.
Moku
10th Solaris Rangers