@Leftovers/Lum Berry
252Hp
Calm/Bold Nature
Prankster
~Calm Mind
~WoW
~Recover
~Taunt
This thing jizzes all over stall and offense. Calm Mind increases your SpD to incredible levels, and its quite easy to get to +2 (one as they switch, one before they attack). Wil-O-Wisp keeps physical attackers cowering in their panties and is your only scorce of damage. Recover to live longer, Taunt to prevent setup/healing. Status is this things worst enemy and Lum Berry saves you once although its probably better to just use Leftovers.
Counters in OU include Heatran, Rueniclus (2 attack versions cant touch you either), Ninetales, Alakazam, Volcrona, Infernape, Espeon and Xatu. If you can get them out of the way, this thing is incredibly hard to kill. Also makes a pretty good lead.