Celebi @ Leftovers
Calm Nature (Timid would've been better)
EVs: 252 HP / 92 Def / 176 Spd
- Calm Mind
- Baton Pass
- Recover
- Psychic / Grass Knot
This is what Celebi is usually used for, considering it's one of the most reliable Calm Mind passers. Psychic is the most popular offensive move Celebi has, but Grass Knot is preferred if it were to defend itself against other threats more effectively.
Celebi @ Leftovers
Calm Nature (Bold plz)
EVs: 252 HP / 212 Def / 44 Spd
- Heal Bell
- Recover
- Leech Seed
- Psychic / Grass Knot
Cleric. Same thing with Aromatherapy on Blissey, it has positive and negative sides. It gets rid of annoying status problems on the team, however, it doesn't do anything to repel opponents at all, and something like a Tyranitar is invited and begins to wreck havoc on Celebi and the rest of your team. If you can afford using a turn to heal your pokémon, then so be it, but take caution, as one turn can really cost you the game at times.
Celebi @ Leftovers
Calm Nature
EVs: 252 HP / 212 Sp.Def / 44 Spd
- Calm Mind
- Leech Seed
- Psychic / Recover
- Substitute / Recover
This is a set of which can make Calm a suitable nature to use. The use of both Leech Seed and Calm Mind can be very annoying, depending on what is being sent out as a counter.
Celebi can also serve as a Swords Dance Passer, that is, if you're ever need of an attack boost granted to your team. You could use it mainly as a sweeper with Choice Specs, or even a SubSeeder. Celebi has many options.