This is a game mod for Crysis. It is currently in open beta and oh my god it is awesome. You've got the Crysis multiplayer way of doing damage to enemies to get money to buy weapons and vehicles, only the vehicles are all enormous tanks and mechs. The multiplayer matches are really pretty cool because they start off with small light mech and tank skirmishes but quickly proceed into assault mech slugging matches. Every time I've looked for online servers, there's always one with at least ten people on it, which is more than I can say for some mods for other games.
cough cough First Strike :(If you have Crysis I would strongly suggest trying this out. The only problem I've had is an occasional crash.
website link:
http://www.mechlivinglegends.net/download link:
http://www.mwlldownload.com/obligatory pictures:

Standard infantry. You can buy a couple different weapons like spotter lasers, pulse lasers, PPCs, and even a bigass beam laser. Comes with jump jets for getting into mechs, and running away.

My personal favorite, the Owens light mech. It's fast and it can sprint longer than almost anything else, allowing for hit and run attacks against larger mechs. The variant I use comes with four Beam Lasers, and three Extended Beam Lasers

The Atlas. Like all assault mechs, it's incredibly expensive, but you get what you pay for.
If you're wondering what's up with the head, that's just a little graphical glitch, there's the roosterpit canopy on the forehead.
I'll get some combat pics next time I play.