S - Falco, Fox, Sheik, Puff
A - Marth, Peach
B - Falcon, ICs, Doc
C - Ganon, Pikachu, Samus, Luigi, Mario
D - DK, Link, Y.Link, Roy, Zelda, Mewtwo, G&W, Yoshi
E - Pichu, Ness, Kirby, Bowser
S & A can probably be fused for compactness. I just figure the top 4 are better at going solo in a tournament but they're similar character quality to the members of A for the most part. Puff and/or Sheik might be arguable as A tier but I think Sheik is about as good as the spacies. Puff I'm less convinced.
I want to put ICs above Falcon but it feels like Falcon is better at staying in the game and there are a bunch of subtle win conditions & weaknesses that ICs have to deal with that Falcon doesn't. ICs having a better MU with Falco & Sheik is really nice though. Doc I think makes sense as third in that group. Maybe he's C tier but his kill power is kind of good if he can hit his KO moves and a lot of them are fast.
Still not sure how to order Ganon, Pika, Samus. Luigi has big moves that kill, which puts him above Mario. Not sure about DK. Kind of feel he's C sometimes because his mobility is way better than anyone in that tier except Yoshi & Roy and he's got a lot of good kill power & some basic combos that work out of throw on basically everyone. But he's also basically a 4-move character with no normals (aside from grab & an incredibly meh d-tilt) so his combat game is super duper limited. I'm not sold either way.
D tier is just a mess of characters that kind of have a few things going for them. E tier is the characters that I feel are basically complete garbage. Don't really care about the ordering of E tier too much.