Very helpful PvP Addons

Deadly Boss Mods-This mod will change how you play wow, you will know what is going on, and how long until it happens again, timers, sound warnings, a must have.
http://www.curse.com/addons/wow/deadly-boss-mods

Battleground Targets-Creates a moveable window with the opposing team on it, it is color coded to class, and can display all of their life simotaneuosly, how many of OUR team is targeting each member, and who is holding the flag. A requirement for RBG's.
http://www.curse.com/addons/wow/battlegroundtargets

Healers have to die-Puts a unmissable red X over enemy players name plate that are healers, makes identifying and chasing down healers no problem. Does the same for healers on your team but the icon is a different color.
http://www.curse.com/addons/wow/healers-have-to-die

PvP Sounds-Adds Quake 3 sounds to PvP or PvE, FIRST BLOOD, DOUBLE KILL, TRIPLE KILL, KILLING SPREE audio as well as BLUE FLAG DROPPED, BLUE FLAG RETURNED. I like this one ALOT.
http://www.curse.com/addons/wow/pvpsound