WowAce

Shows mana usage as a percentage in a spells tooltip.

Collect data about you myth+ challenges

Enhancer

Display Garrison missons for all Characters

Adds party/raid role icons in useful places

This will keep track of how much you have paid per item in your inventory. Only one of (Auctionator, Auctioneer, AuctionLite,...

Tools for MultiBoxers or Group questing/leveling

Nihilum Raid Tracker, originally written for the EU guild Nihilum.

Searches bags/banks of all your characters/guilds.

Tracks the current Fear Ward's in the raid or party.

Adds predicted lists for spells while the user types

Displays online guild mates.

A library to provide a clean dropdown menu interface.

ItemSync the happy item gatherer and toolkit.

Rebuff yourself with the mousewheel.

Insanity resource tracker for shadow priests.

Detects specific CDs and spellcasts

Death reports

eeShards

Add-on that shows in a unit tooltip window a number of killed mobs of the same kind