While right now I can't think of any annoying Pokemon to fight against in-game(Bar Whitney's Miltank and Juan's Kingdra), here is what I ran into yesterday in Ubers:
Smeargle @ Focus Sash, LEVEL 1
Liepard @ Leftovers
Moves: Substitute, Nasty Plot, Assist, Dark Pulse
While I did have priority, Sleep Clause has been deactivated until May 31st(only for ubers), and this is what trolls can do.