Pokémon Ribombee

[Celesteela]

I do think it's worth mentioning that at 124 speed, Ribombee is the fastest Fairy-Type available in the meta game. Does it outspeed any notable scarf users?

Does Tyranitar count?

 

[tomtom5858]

Does Tyranitar count?

164 SpA Ribombee Bug Buzz vs. 0 HP / 0 SpD Tyranitar: 150-176 (43.9 - 51.6%) -- guaranteed 2HKO after Stealth Rock

That's actually a pretty cool KO, catch it on the switch-in, then 2HKO it while it thinks it can outspeed you. QD isn't really a big help, though.

+1 252+ SpA Ribombee Bug Buzz vs. 0 HP / 0 SpD Tyranitar: 260-308 (76.2 - 90.3%) -- 18.8% chance to OHKO after Stealth Rock

Still, get a bit of passive damage on the thing and it'll drop to a +1 Bug Buzz without any trouble.

 

[Plasmirror98]

Whilst Ribombee isn't the bulkiest, it still has a couple of neat resistances. 4X fighting and 2X ground come to mind.
As mentioned before, a ground type partner would help. Ribombee can't do much to steel-types.

I do think it's worth mentioning that at 124 speed, Ribombee is the fastest Fairy-Type available in the meta game. Does it outspeed any notable scarf users?

Max speed Ribombee hits 381 Speed, which according to this list is a single point slower than Adamant Scarf Diggersby and +1 Feraligatr.
Also Koko is a faster Fairy (and Scarf Lele), but if we're talking UU the next fastest would be Whimsicott.
Speaking of its resistances...
252 Atk Life Orb Pheromosa High Jump Kick vs. 0 HP / 0 Def Ribombee: 108-127 (41.3 - 48.6%) -- guaranteed 3HKO
Obviously you're dead if it has poison jab and U-turn is always there, but Fun Fact.

 

[Zé Capáu]

Also Koko is a faster Fairy (and Scarf Lele), but if we're talking UU the next fastest would be Whimsicott.

If you're talking about Prankster, then Whimsicott is even faster Fairy than any Tapu, otherwise it is slower than Ribombee (116Spe < 124Spe).