Man, Game and Watch is a great character and I am happy to see him at what we will assume is the top now ^_^. I always wanted to make him my main in Melee, but he was just too light and had a very, very crappy shield, very slow roll, mediocre spot dodge, not very useful throws (mildly so), among his other faults, and now they buffed almost every attack in his arsenal PLUS gave him a bright baby blue costume to annoy the piss out of a lot of people due to how much it contrasts with the rest of the game... I just didn't have the balls that DireVulcan had, haha. Anyway, I wanna discuss a few of his moves at length (I told you guys I wanted to say a lot about GnW, and maybe this is too detailed, but even if it is, it's fine. At least in my opinion ^^).
EDIT: Sorry if my text looks a little rushed, I tried to make it as detailed as possible but I didn't have anything prepared before I saw this thread open and I'm really eager to get this information out).
Character Summary
If you don't want to call Metaknight the new Sheik, then give that title to this subhuman being from a universe of only two dimensions. His attacks practically blink out due to his overly cartoony and liquid crystal game-based nature, and this makes every one of his attacks very quick to execute. Moreover, most of his moves end swiftly too, which means it's hard to punish a good Game and Watch (most noticeable moves to punish are f-air and f-smash, but even the f-smash is still an amazing move). Because he uses toys and other objects to attack most of the time, almost every move he uses will have decent to exceptional priority as well. Excellent recovery, and having an excellent recovery while also being one of the floatiest characters in the game means you've got a great edge game. His only drawback is his weight, and maybe his grab range or something. Also, his Manhole (d-tilt) was nerfed, sadly. If Game and Watch fails to maintain Top/S tier status I'll be surprised, and if he ever dips below Upper/A tier, I'll be shocked. Anyway, onto moves:
Dthrow
Among the things LeeHarris said about Game and Watch's dthrow, the move just gives him tech chasing opportunities like almost no other character has in this game, and for those of you who honed your tech chasing using Sheik, Falcon, Fox, among others in Melee, one of Melee's best tactics can be reapplied in Brawl amazingly well here. Dthrow into <move> is good, like dsmash, dtilt, ftilt, et cetera, and a lot of times it's one of the first things you start using, but if you can predict someone's techrolling patterns you can repeatedly grab them and eventually land a move that really hurts. Most people avoid Game and Watch's dthrow into dsmash by just rolling at the right time, which is possible even without teching. But if you force them to mix up their techrolling, you increase the chance that on one of the dthrows they will simply wait a second before rolling out or teching in place, which gives you the dsmash. Good tech-chasing is a scary thing against a good Game and Watch. In some matches, I've gotten around 50% racked on via dthrow tech chasing depending on their character, and that's before considering what a dthrow to bucket can do to them (usually death unless it's quite a heavy character at below 20%).
Dash A
As we should all know by now, Game and Watch has preserved his insane priority on a lot of his moves, in fact - pretty much all of his moves, as LeeHarris pointed out with his key, but his dash attack has a significantly ridiculous hitbox considering the part of his body he's using. The dash attack can cancel every projectile except Rob's and Wolf's laser, Olimar's Pikmin, and one other character (i can't remember) so it's a great move to use if you see a projectile flying out while dashing, as you maintain your position with no move endlag. This move also clanks with TONS of actual attacks including many smashes, so it's a move you can truly safely throw out in a match. The thing I like to do is use it against a shielder and dash attack early (before being within grab range) and if they try attacking me, it's almost a 60% chance that it clanks their attack (it depends on the character and the specific attack they use). Being within this close proximity gives Game and Watch his chance to attack with one of his very fast and/or powerful moves, like d-smash, f-smash, d-tilt, f-tilt, neutral A (VERY fast), etc. It's just a move that a lot of people probably underuse, but it shouldn't be overused due to the inherent risk of being shieldgrabbed.
Turtle
Certainly his most useful move by far, with its reach, priority, ability to eat shields, and very low endlag. I am sure this move is going to be discussed ad nauseum, and already has been brought up multiple times so I won't dig into it, just mention that it's really good.
Trampoline (Up+B)
This move is ridiculously weird sometimes. Due to the parachute you get after you use it, it's just a ****ing great move to use to edge-guard and try to get a horizontal KO (Game and Watch relies on horizontal KO's for everything except his upsmash). The last time I played against KishPrime I got at least two KO's with this move (not the same matches) and he was surprised. Also, if this doesn't kill them, depending on the character weight and their percentage, you can sometimes land a fair afterward (although that's slightly risky due to losing the parachute). But I have followed up with the fair and made it back safely, you just have to remember to be close enough to the stage.
U-air (wind...yness?)
This move is just downright hilarious while still being effective in its own way. While you won't receive a lot of kills with it, it can stop projectiles, severely frustrate the landing of many characters, and can also lead to potential kills with other moves, or if nothing else lead into another attack. While the airdodge does avoid the vertical boost, air dodging can be a bad thing for them to do if they do it at the wrong time and let you hit them right after it's over. The move also halts the downward momentum that many characters receive from their d-airs. Hurtling projectiles back into the air and stopping a lot of good anti-air moves from connecting make this move a great juggling move. A weird but nonetheless interesting property of his uair is that even if it doesn't connect, the wind alone has the ability to take back your costume from Kirby, or at least that's what I concluded through testing it in matches.
Bucket
I don't know how often this move was used in Melee, but the bucket in this game is absolutely FIERCE. No character wants to give him a free bucket by spamming energy projectiles, and if they get hit with it, it can KO almost anyone at 0%, and still gets tons of KO's at amazingly low percents even with DI. Does about 62% to Zelda after receiving her Din's Fires, similar damage from Pit's arrows. Apparently also absorbs the stars from Dedede's up B and Yoshi's down B, which isn't that useful but still fun to know. The invisible range of this move is just insane too, it can reach a large area that completely surrounds him, which means that if you pull out a bucket on an energy projectile, you're always going to catch it before it hits you unless you just don't pull the move out before it connects with your character. And as long as you keep your distance while using this move, you aren't at a lot of risk, since most people that throw a projectile at you are from a distance anyway. I know that if I have 2/3's of a bucket saved up and I'm not at a very high percent yet, I'll gladly trade receiving a smash for the final third. This move is so fast and stays out for so long that if your opponent isn't being very careful at avoiding it, they are going to die. Did I mention that you keep whatever is in your bucket if you lose a stock?
Anyway, this is all I can think of wanting to contribute to for now, maybe I'll pop back in here in a couple of days and discuss how he goes about mauling some of the best characters, and who he has trouble against.