Marian Hegemony III Legio Longbow

The Hegemony actually has no unique mechs (unless you count those weirdo MilitiaMech Centurions), but the Longbow might as well be their unofficial mascot. Specifically, the LGB-0H, which swaps the lasers for a pair of PPCs, adds a little extra speed, and strips out all the missile tubes to replace them with two hundred and sixty rocket launchers, which it can fire simultaneously (albeit at the cost of basically automatically shutting down for the rest of the game).

Its worth noting that the Hegemony actually does get access to plenty of regular and vastly more sane Longbow variants in just about any era, but let's be real, you don't play the Hegemony to be sane.

Pax Mortis