Mechwarrior 4: Mercenaries
"* " Get MekTek. Then get NetMech IV. Actually, I think you can get NM IV and it'll download Mektek with it. Either or, hundreds of mechs added, tons of weapons, maps maps maps, and people still play online religiously.
- Your 'mech must have at least 2 heavy lasers and 2 PPCs. After that, do your thing.
- Everyone is a jump-jetting PPCing whore. Plan accordingly. I recommend "missile-boating", i.e. stacking your mech with a fuckton of missiles and bombarding from afar as soon as one of those beam-spamming nutjobs pop their little cockpits over the visible horizon.