Must have addon : GTFO

Get it here

GTFO provides an audible alert when you're standing in something you're not supposed to be standing in. In some cases, you'll be warned before you start taking damage. This mod improves your situational awareness and is recommended for dungeon divers and raiders of all skill levels as even the most seasoned veteran sometimes needs a reminder to GTFO.
It's particularly useful for individuals that play with their spell graphics turned down as well as assisting with PvP when you can't tell who's casting the AOE.

What is your Fav Addons ?

DBM and Healbot... but what else are people using... I downloaded Quest Completed to help in Deepholm and my missing 55 quests - post your comments - what is it and why ?