There is Mechwarrior 2 for the Mac, and two other, that I can't remember the names of. One is like Mechwarrior, but has only the fighting, and the other is like an anime style mechs with over the shoulder (Tomb Raider)style.
Mechwarrior 2 is the missions and the fighting, but the graphics are old, non-textured, flat sided style with the maps being deserts, mountains and lego style bases, while the others have texturing on the mechs and the maps. The anime (Shogun?) game takes place deep in a huge mega city and sewer system.
Overall, even though the later two mentioned have textures, they are simple hunt and shoot type games, while mechwarrior, having lame graphics, still is a precise, calculated game of missions and mayhem. I just wish the game developers would port the later mechwarrior games to the mac, so we can have the eye candy too.
Eric