Well, I noticed that we're supposed to discuss sets so here goes (in no particular order).
OldJack, Alexander and ala, all of you posted sets in the on-site analysis. I assume this was unintentional, but it doesn't really fit with the goal of this project.
youngjake93, your set is good defensively against Sun, but it seems to compormise Celebi's effectiveness against Rain, one of its main selling points, a lot. It isn't bad against Rain, but it will be helpless against certain Rain 'mons like Ferrothorn, as well as other Pokemon like LumDD Dragonite/Salamence/Haxorus. Also, mono-Grass coverage sucks against Sun, with the abundance of Fire- and Grass- types, as well as things like Xatu and Dragons.
scorpdestroyer, Rest Celebi is good in theory, but I know from my experience using Shaymin that Recover > Natural Cure Rest, because you can stay in after you heal. The moveset is exactly what I would use with Rest though.
Homeslice, Sunny Day Celebi seems like a neat idea, but it would be hard to fit on a team. Weather teams other than Sun won't run a conflicting weather move, and weatherless teams already tend to have the hardest time against Sun to begin with. Sun teams also would have a hard time running it, but the typing stacks weaknesses with Chlorophyll sweepers, as well as other common Sun Pokemon like Xatu and Dugtrio.
H-C, Baton Pass Celebi sounds like an interesting idea. My only worry is that you would need to make sure anything that could revenge your sweeper is KO'd, and this Celebi has diminished utility outside of Baton Pass.
BlackLight, Your Baton Pass Celebi sounds like a better idea. The increased offensive coverage lets it be less one-dimensional, and SubPass can benefit a wider range of Pokemon. I'd still be wary of using Celebi over something like Mew for this purpose, because of the amount of weaknesses.
Neliel Tu Oderschvank, you have the best Baton Pass Celebi here, as well as one of my favorite sets. I've always liked Baton Pass Pokemon that can sweep and use Baton Pass for when their sweep is threatened, as opposed to dedicated Baton Passers (outside of full Baton Pass). Physical Celebi also sounds like a good idea. The unexpectedness is a huge plus, as most only consider special Celebi. It might also let you get two Swords Dances, when the opponent switches in something with special bulk like Blissey, and then switches out when they discover that Celebi is physical. Sucker Punch is also great for Celebi and vice-versa, turning its weaknesses to an advantage by provoking attacks.
You just went and posted the most hellish thing I have ever seen in the history of Pokemon, right behind Swagger+Thunder Wave Sableye in hail.-- BlackLight, speaking of my Gravity Jirachi.