If you want a strangely awesome 'Mech game that shows what very early Prototypes would act like, go collect Ring of Red
for PS2; each AFW (Armoured Fighting Walker) Is big, lumbering, slow, uses a HUGE diesel engine and oodles of hydraulics to move, and only has one or two guns on the entire frame.
There's four basic types, too; General-purpose, which is bipedal, has one big gun and one arm to punch things with. Scout, which looks more like a small boat with a turret slapped on top and legs, but is stupidly fast, can be knocked around easily in combat, and shreds infantry. Artillery, which are Four-legged monstrositied carrying 6-inch howitzers as their main guns, and up to 2-inch cannon as their anti-infantry guns. Great at long range (duh) but slow as hell and lightly armoured. And Finally, there's the Close-Combat Unit, which has a pair of bludgeons for arms, and reinforced hydraulics to use them to pound holes in enemy walkers; Best used up close and personal as their guns are large-bore shortbarrels.
Though, the main character does happen to use a Prototype with a german-made 88 mm cannon for a right arm, and named it 'White Tiger'
You might like it.