Encore / Sub 3 attacks Alakazam are actually pretty fun to play, but the amount of Blissey/Scizor/Jirachi is too damn annoying, B- imo.
I'm also pretty shocked by how low-ranked Snorlax and Roserade are:
Snorlax: An underrated mon but still a pretty good switch to a lot of things like Starmie, Zapdos, Heatran, Suicune or Blissey...I like refering him as an "offensive oriented blissey" and it's a good support for Balanced / Bulky Offensiv teams. The choice band variant is quite fun and can get some nice kills by trapping Starmie/Gengar/Offensive Rotom-A, (too bad it can't have pursuit+selfdestruct damn) and the Curselax is still a threat for some teams that lacks physical fighting-attack (Scizor/Lucario/Heracross are pretty weak to Fire punch on the switch too)
It deserves to be A or A- at least imo.
Roserade: The fact that Roserade is ranked lower than Venusaur is shocking for me. Roserade is the only viable mon in OU who can set-up Toxic Spikes, and he can do that pretty well as a lead. It is also a good support Pokémon in a Fire/Water/Grass core, checking things such SubRoost Zapdos, Jolteon, Starmie or Breloom pretty well, it is also one of the rare viable Spikes user besides Skarmory and Forretress. I admit he is not really threathening as a sweeper but the timid+spikes/LO version are actually not bad and a stabbed leaf storm is quite scary.
A- for me.
Celebi is also pretty overrated io, while being a good Breloom check/Baton pass user, his movepool and his typing makes him in danger in a lot of situations, U-turn teams like Scizor/Flygon/Infernape can play with him even for the Tinkerbell version with no problem.
He is also outshined by Roserade who got Spikes and a better typing for the defensive grass-type and Shaymin which is a way better offensive grass-type for two reasons: Seed flare and no x4 U-turn weakness.
A- or B+ for me, and Shaymin deserves to be A too, it's an awesome stallbreaker and offensive/balanced teams without Skarmory/Scizor+Zapdos/Dragonite will have a tough time checking it.