I played RIFTS(C) for several sessions a few years ago. I had a Glitter Boy; my soon-to-be-girlfriend had a cyberknight; the GM's wife was playing a young elemental wizard; and among our three other friends, a techno-wizard, a were-lion, and a dragon.
The Glitter Boy's main armament is the Boom Gun. For the uninitiated, it's a hypervelocity electromagnetic gun firing a flechette round. I could fire that puppy three or four times a combat round, but I didn't use it often, despite it being one of the more powerful power armor weapons in the main book.
In one of the earliest combats that I can remember, we had ventured into the ruins of DC to raid the remains of the Smithsonian. As I recall, a leather aviator's jacket that we found on one of the dummies there eventually sold for a mountain of cash. Anyway, we got into a fight with another group, practically on the steps of the capital.
I was thinking differently, trying to think modernly, because in FRPGs I have noticed a tendency to go toe-to-toe with enemies and then not budge out of your square until you have to move to reach more enemies. So I wanted to try a more fluid sort of combat with RIFTS, and I moved my mecha over behind a ruined car, for cover, despite being only covered from the waist down, I was so tall in the Glitter Boy.
And I unshipped my Boom Gun.
So my next action came around and I took aim at one of the bad guys and pulled my trigger.
Now, the thing about the Boom Gun is that its hypervelocity round breaks the sound barrier several times over. The Glitter Boy deployed pylons and has reaction jets to counteract the force exerted. So I was stuck in the ground.
I was the only one.
The sonic boom picked up the car I was standing behind, flung it down the street, knocked all the remaining glass out of any windows along the shot, deafened all of my allies, and only did a few points of damage to the target.
So that wasn't a good match.
As several people have said so far, RIFTS needs a GM who can handle widely varying power levels. My GM responded to the whole deafening-my-party problem by allowing the technomancer to make and distribute earphones that would negate the deafness from my sonic boom, as long as the person wearing it had ISP or Internal Strength Points to spend. These headphones cost 25 ISP every time I fired that dumb gun. Everybody in RIFTS has some ISP, but very few people have a lot, so that turned my boom gun from a never-use-it to a bust-it-out-on-the-BBEG-but-not-before. So I ended up running around with a laser rifle modified so's my butterfingers mecha could use it.
Oh, and there are 9 or 10 stats which don't affect anything unless they're 16 or above, except if they're very low, when you get into penalties. But basically everything from a 6 to a 15 in any stat is exactly the same. I think there are some rules for rolling against your stat to accomplish some things, but it's unclear whether you roll on a d20 or on 3d8 since all the stats go up to 24 or more.
So it really needs someone to make judgment calls and be able to head off rules arguments. Course, it helped my group that none of us but the GM knew the rules very well.
TWK