Time to add some personal experiences ;p
I've only added the characters that i've played against a decent player with.. <-that sentance isn't good english but oh well xD
WALL OF TEXT INCOMING
Marth: Downtilt his upB, eruption works too but timing is tight.
Game and Watch Don't have a clue.. his recovery is to good imo.
Luigi: Dair predict his ->B, or just wait at the edge and downtilt him since he doesn't snap to the edge. ALSO reverse aetherspike pretty much pwns him.
Falco: downtilt his fatasm, it works I've used it. Timing is near impossible though ;p, his firebird needs no gimp..since it never reaches the stage.
Ganondorf: I usually Fair his recovery, it outranges pretty much his entire air game, and when hit right he's done for.
Wolf: I usually Fair him too, but it is possible to stand at the edge and just downtilt, since his moves sometimes 'bug'. He can be Daired, and reverse Aether works nice too.
Lucario: Since his upB does no damage, I usually just hang on the edge ;p I have yet to face a good lucario though.
Ness: Reverse Aether might work(?) don't know if it is able to bypass his PKmissle though (prioritywise)
Toon Link: edgehop->counter should work, but reverse Aether just does WONDERS ;p I know this;p
Robot: if he flies over you, aetherspike him, if he goes from down the stage, just dair him or Aether-stage-spike him. What a word...
Captain Falcon: -
Jigglypuff: -
Diddy Kong: his ->B is vunerable from above so dair / reverse aether works. upB is kinda hard since his barrels can stagespike you.
Pit: depends, if you see him us upB immidiatly hit him out of it, Fair works, or a predicted Uair. If he tries to go under the stage, run of the stage, fastfall and aether back. The aether hit should stagespike him and kill him.
Meta Knight: .... never got around to trying to gimp him, was always the other way around ;p Dair his nado, is mad fun^^
Pokemon Trainer: -
Ike: a well spaced Fair outranges his Aether, counter works too if timed right.
Snake:
King Dedede: reverse aether does wonders, and if he upB's you can even aether him again from downunder.
Sonic: -
Wario: -
Captain Olimar: one fair during his doublejump is an instant kill, just grab the edge after the hit and olimar lost a stock.
Lucas: kinda same as ness.
Mario: -
Donkey Kong: Dair from above works, since his Roflcopter is very vunerable from above. But don't know if reverse aether has enough priority to go through it, it should though.
Link: Edgehop -> Counter pretty much destroys his recovery. A stagedrop Fair also usually screws him over.
Samus: Imo very hard to gimp, never got it right;p
Kirby: -
Fox: -
Pikachu: if he's stupid enough to use ->B as recovery, punish him with...well every spike pretty much destroys it. UpB is near impossible to spike but a retreating Fair can hit him out of it resulting in another try to recover.
Zelda/Sheik: -
Peach: -
Yoshi: -
Ice Climbers: -
Bowser: spike his upB with your dair or reverse aether, pretty much same as DK when it comes down to possibilities. Do watch out for a predict, if he sees you coming he might Bowsercide you instead of his upB ;p
Zerosuit: her sideB is just begging for a spike, and she's got the same 'deathspot' as ike. If she's left/right side UNDER the stage, a good edgehog will kill her. Walk off Fair should kill her, since it brings her out of range of the edge.