Nidoqueen is an excellent Pokemon in nearly all formats including OU and there's more than 1 set you can use.
Scarf works well in RU/UU but not OU - Nidoqueen just doesn't have the power to justify it, but with Sheer Force it does pack a nice punch. Specs can be used in OU but only late game and only if you have tailwind/sticky web support.
Life Orb with Stealth Rocks is great in every tier.
