A new tier list has emerged for Smash Bros 4 Wii U. A few changes have taken place, most notably being that Bayonetta has been knocked down a spot and no longer occupies an S tier spot anymore.
The tier list was made by conducting votes by players from the site Smash Boards. As such, you can consider this one of the more well-rounded tier lists and possibly as official as you can get when talking about tier lists. Mostly because usually when tier lists release for fighting games, they usually reflect the views of just the one person who made the tier list.
To that extent, you can check out this well-rounded tier list here below (You can click on the image to view its full resolution).
Here's a list in textual format for Super SSB4 Tier List:
S Tier: Diddy Kong, Cloud, Sheik, Rosalina, Mario, Sonic, Fox
A Tier: Zero Suit Samus, Ryu, Mewtwo, Bayonetta
B Tier: Pikachu, Meta Knight, Villager, Mega Man, Ness
C Tier: Toon Link, Corrin, Marth, Captain Falcon, Greninja, Lucario
D Tier: Yoshi, Pit, Donkey Kong, Peach, Dark Pit, R.O.B. Luigi
E Tier: Olimar, Robin, Browser, Lucas, Wario, Ike, Lucina
F Tier: Mr. Game & Watch, Pac-Man, Palutena, Kirby, Duck Hunt, Link
G Tier: Shulk, Samus, Wii Fit Trainer, Browser Jr., Dr. Mario, Falco, Roy
H Tier: Charizard, King Dedede, Zelda, Ganondorf, Jigglypuff
Official 4BR Smash for Wii U Tier List v2.0
Source: Smash Boards