omen or KLH threatmeter - for threat management
omnicc - cooldown timer
milk sbt - for triggers, spell/skill alert and enemy gains
x-perl - unitframes
cartographer - for easier map navigation
bagnon - all ur bags in 1 window
advance trade skill window - easier navigation for profs
gatherer - for harvesting type profs
bartender - customized action bar
damage meter - for dps epeen flexing
auctioneer - for AH
deadlyboss/bigwigs - for boss announcements/triggers

thats what i usually use regardless of the class.