Not sure how some of you guys are coming to your conclusions. Spikes aren't great if you can't set them up or combo into them.
Spikes
Mario -
Luigi - Down Special, Down Taunt
Meteors
Mario - F-air (Meteor)
Luigi - Down Special (Spike) Down Taunt (Meteor?) D-air (Meteor)
Bowser - D-air (Meteor)
Peach - D-tilt (Meteor)
Yoshi - D-air (Spike/Trade) F-air (Meteor
Rosalina - D-air (?)
Bowser Jr. -
Wario -
G&W - D-Air (Meteor)
DK - Side Special (Spike), D-air, F-air (Meteor)
Diddy - Side Special (Spike), D-air (Meteor)
Link - D-tilt, D-air (Meteor)
Zelda - D-air (Spike sourspot, Meteor sweetspot)
Sheik - D-air (spike)
Ganondorf - D-air, Down Special (Meteor)
TLink - D-air (Meteor
Samus - D-air (Meteor)
ZSS - D-air (?) D-special (Meteor)
Pit - D-air (spike)
Palutena - D-air (?)
Marth - D-air (spike)
Ike - Up Special (spike), D-tilt, D-air (meteor)
Robin - Up Special (spike), D-air (bronze spike, Levin Meteor)
Kirby - Up Special, D-air (spike)
DDD - D-air, Up Special (meteor)
MK -
Little Mac - D-air (spike)
Fox - F-air (spike)
Falco - F-air (spike) D-air (meteor)
Pikachu - B-air (spike)
Charizard - D-air (meteor
Lucario -
Jiggs -
Greninja - D-Air (?)
DHDog -
Rob - D-Air (meteor)
Ness - D-Air (meteor
C.Falcon - Utilt (spike), D-air (meteor)
Villager - D-Air (?)
Olimar - D-Air (meteor)
WFT - ???
Dr. Mario - ???
Shulk - D-air (meteor)
Pac Man - ???
Mega Man - D-air (?)
Sonic - D-air
Mewtwo - D-air (meteor)
Lucas - D-air (spike), B-air (meteor)
Roy - D-air (meteor)
Ryu - D-air (meteor
Known(to me) combos into spikes.
Mario - Dthrow, Fair. Uair, Fair. Dair, Fair.
Diddy - Dthrow, Dair. Uair, Dair. Banana Dair
TLink - Bomb, Dair
ZSS - Down Special/Neutral Special/Nair/Dsmash/Dthrow into Down Special
Kirby - Fthrow, Up Special
Falco - 1Frame Dair, Dair
C.Falcon - Dair, Dair. Uair, Dair/Utilt. Dthrow, Dair
Lucas - Dthrow, Bair
Ryu - Dair/Nair, Dair
Objectively the best meteors in the game as far as I know have to go to Falcon and ZSS for being extremely easy to combo into in most situations (neutral, punishes) with no escape with even the best DI. Mario comes close, but with the right DI it's a 50-50
As for spikes, there aren't many comboable spikes that I know of are by Kirby and Falcon. Kirby probably has the best spike in the game though. Not only because it's a great edgeguard tool, but because it's one of the best combo starters in the game.
If the thread was for most powerful spikes then I'd have to say Ganondorf since it has electrical properties and is probably the most satisfying to land and leaad into a 2 hit, 38+ damage combo at low to mid %s