Some of G&W's aerials are nasty as hell man. He also owns one of the only moves that start on the very first frame, his up-B. I know it isn't a killing move, but it's something to think about. The only other moves that start on frame one are the shine and the rest.
G&W's oil panic is pretty interesting too, considering it's power is proportionate to that of your opponents projectiles. One day there will be a successful ness and G&W team that uses the oil panic + PK flash oh so well. It'll happen, maybe.
His side B is also unique because of how lucky you gotta be. I also enjoy studying the rules of how it works, it's pretty interesting, and a potentially match-turning last resort.
With all of his disjointed hitboxes, and unique B attacks, one would think he would be up there on the tier list. But alas, his lack of L canceling on 3/5 of his aerials really seems to shut him down. And when I say shut him down, I mean that it makes nobody want to play him, which in turn results in him falling down on the tier list.
His uair is negligible in my opinion, which means you don't have to worry about it not being L-cancelable. His dair is pretty useful, and is apparently a meteor smash on one of the hitboxes. As long as you land the right hitbox, then you shouldn't worry about your opponent punishing you for lack of L-canceling. The same priniciple goes for the nair, which is objectively the best nair in the game. It's like a ****ing shield of it's own, and has fantastic knockback!
He also has crazy tilts. Up tilt is so spammable and down tilt has unique range and good knockback.
In the end, g&w is a pretty okay character, and is by far the most underrated in the game.
I go on too much about things :|