ElvUI/TukUI

ElvUI and TukUI are full user interface replacements for World of Warcraft, which means they completely replace default UI. You can customize every single part of your UI to your liking. ElvUI is a more user friendly. TukUI requires you to do more work to get everything just right.

Abyss UI

AbyssUI is a minimalist World of Warcraft interface. It changes parts of the interface so you can have a more customizable and clean UI. The goal was to have a high customizable interface that changes little of the wow artwork or functionality.

GW2 UI

GW2 UI is based on the Guild Wars 2 UI and aims to increase immersion and efficiency. The entire UI is hand-painted, and hand-coded. Each interface element has been (or will be) rewritten, to provide enhanced functionality as well as improve the user experience.

HydraUI

A visual interface replacement for World of Warcraft. It restyles the default interface, while adding many useful features. It requires no setup, and is configurable in-game.

LS UI

Yet another UI, but this one is a bit special. You can choose an Orbs or Classic bar layout style.

nUI

100% standalone code designed to feel like Bliz meant the UI to look this way. nUI removes a ton of clutter from the display, provides detailed targeting information, an integrated HUD, cooldowns and more all in one tightly integrated single-source addon that requires no user configuration.

RealUI

AddOns Included: BadBoy, Bartender4, Clique, Grid2, KuiNameplates, Masque, MikScrollingBattleText, PhanxChat, Raven, Skada

Shestak UI

A modular, lightweight, all-in-one overhaul for the World of Warcraft interface. Aims to streamline and clean up the interface, removing unnecessary frills and wasted space while filling in some of the holes left in the default UI.

Uber UI

Designed to be a super lightweight addon to darken the default WoW UI.

ViksUI

ViksUI is a fully functional UI replacement for WOW with many extra features that are not included in the standard UI. Almost everything can easily be changed in-game. Panels and borders can have colors on, or turned off.