giving your whole UI a facelift

I've personally never been much of a fan of cosmetic UI addons, but I'm a big proponent of utility addons and feel like they can improve your performance dramatically. Therefore,

Little Empire Mojo

I won't really be talking about unit frames or action bar replacements because frankly I'm not very current with them.

d3 items

If you're interested in giving your whole UI a facelift, you may want to look into an all-in-one solution such as ElvUI,

buy kingdoms of camelot gems

or check out WoW Insider's addon spotlight. Let's start with the addons I can't imagine playing my hunter without.