MechWarrior 4: Black Knight

From Microsoft Games:

You're back on Kentares IV, and this time, you don't have to play nice. Enlist in the notorious Black Knight Legion, climb aboard any one of five new 'Mechs, and deliver some payback for all the injustices you've been dealt. Put your mercenary skills to the ultimate test in a world ravaged by civil war. Use the new Black Market feature to get the equipment and weapons you need, when you need it. Go Mech-to-Mech with friends and foes alike in the multiplayer-only MechWarrior 4: Black Knight trial version. Fight on a team or go it alone in Absolute Attrition, or team up and try to destroy the enemy HQ in 'Mech Strongholds. All the action takes place on a Volcanic Map, so heat is a big factor. Featured 'Mechs include the new Ryoken and Sunder, along with the "jack of all trades" Bushwacker, the deadly Mad Cat Mark II, and the fearsome Atlas. You'll have all of the weapons except for Cluster Bombs at your disposal, so have fun.