Scary things:
With Cresselia, Umbreon, Gligar, Gastrodon, Milotic, Celebi, and, of course, chansey usable, stall looks good.
Drought also scares me, especially Charizard.
Baton Pass has Mew, Smeargle, Jolteon, ninjask, zapdos, Ambipom, and gorebyss usable. Scary as well.
The only question is, what to use?