Theres a special place in my heart for Battletech. Friends dad was huge into it when i was in 3rd grade back in '88. I still remember using the Hunchback as my first unit.
Ah the hours upon hours of making custom mechs. I even have Heavy Metal Pro so dont have to do them by hand.
MegaMek.net is great for fans of the original pen and paper game with the minies.
http://www.mekwars.org/
Excellent ongoing campaign pitting all the houses and mercs against each other for control of the inner sphere. Havent played in a couple years because of lack of time having a 3 and 1 year old.
What i really want is a tactical game of Battleforce for the PC. I would be all over that. Make the entire army the focus with a sprinkling of mechs, just like it should be since they're rare and all.