RECOUNT

Recount is used mainly by dps to show how much damage per second (dps) they are doing in mob and boss fights. It will show everyone's dps in your group or raid. It can be an invaulable tool in helping you improve your performance.
Recount also shows - damage taken, and healing done - as well as many other functions.

wow.curse.com/downloads/wow-addons/details/recount.aspx


GTFO

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.Healers will love you if you can avoid ground damage from AoE effects - and this addon will help you do that.

wow.curse.com/downloads/wow-addons/details/gtfo.aspx