Bucket is extremely good against Zelda and PK boys, and is broken nonsense in teams. Bucket also gives DDD, Pikachu, Pit, and ROB significant problems.
Also, you're not going to PS it on reaction if the G&W is smart. What G&W wants to do is use it out of shield. =)
The bucket is not very good against Ness and Lucas; it's one of those things that sounds nice on paper at first but really just doesn't work well. Bucketing the tail of Pk Thunder, the most common way to bucket it against Ness/Lucas who actually know how to steer the thing, sets you up for Pk Thunder 2 quite often (it's actually laggier than being hit by it) and gives you a minimum power bucket even if you fill it, and only stupid Ness/Lucas will let you get Pk Flash, Freeze, or Fire other than Ness's weak fire pillar once in a while so they aren't a big deal. The gimp is not that good either since both are pretty good at recovering without Pk Thunder (Lucas basically never needs it so the gimp might as well not exist with him), and either way actually moving Mr. Game & Watch to the gimp position before they start using Pk Thunder is not going to be possible very often; thinking it will happen all the time is kinda like thinking that every time Olimar ever has to recover in any way he'll be gimped. The bucket is still a really nice thing to have since it acts as a deterrent to long range Pk Thunder attacks, but its power as a deterrence is really the best thing about the bucket against those two (mostly Ness since Lucas's Pk Thunder is mediocre at best).
Smart R.O.B. players make it a real pain to use; they just switch from laser -> gyro to gyro -> laser and will stick with the weak laser more so even if you can bucket it it doesn't help you all that much. I find it's actually pretty decent against Falco, Wolf, and Lucario on top of those you mentioned though (not "really good" but "decent"). I agree that it's pretty nice against those other characters though; it's too funny to force King Dedede to keep an eye on the Waddle Doos. Just don't let him sweetspotted fsmash you when you get too excited over the bucket (getting too excited over the bucket leads to early deaths in every matchup actually). Of course, the bucket is also top tier on Corneria, but we all were already aware of that I think.
As a general point, for those who haven't thought about it, 1/3 of an instant kill bucket is worth taking 10-15% damage for. If they hit you out of the absorption lag of you getting a good projectile, it's very plausible that you actually won the exchange. The last absorption is extremely fast too so you only have to eat two hits to get a full bucket "the hard way".
Oil Panic out of shield at that super close range is generally effective, but the long range hit is only going to work out of a standard shield if you just blocked something silly like a sourspot fsmash from King Dedede that gives you a huge advantage. It's important to distinguish between Oil Panic's hits because the speed and range difference basically means that you use it like two different moves. Of course, Oil Panic out of powershield in almost any context is just amazing. I also like Oil Panic off a ledge; it's one of those attacks that goes through solid objects so it can really catch people like that.
