The worst Pokemon move (aside from Splash) would have to be Growl or Tail Whip. Everything and their mother has this in game, and it's fairly useless when you use it. :/
Unless you're in a double battle, because it affects both foes.
Someone on some previous pages mentioned the multi-hit moves... True, the Skill Link ability helps, but those moves are also really useful on a Cinccino with Technician, since each hit gets a power boost. Especially if it's Bullet Seed, which is also 100% effective. Normal-type multi-hit moves like Fury Attack and Fury Swipes, on the other hand... not so much.