I made a whole thread about NU Pokemon that function in OU: http://www.smogon.com/forums/threads/never-used-or-are-they-a-top-10-list.3492205/
But anyway, here is one Lower Tier threat from it:
Ludicolo
When countering rain teams, most people look to Gastrodon, or Rotom-W. But, hidden in the...