So, what addons are you running, and which ones do you think are critically important to enjoy WoW like you do?
Personally, I don't use too many addons, but still I think that bigwigs, GTFO weakauras etc are more or less mandatory to be able to PvE efficiently. (Plus, raiding tools and loot addons to help work together as a team when raiding.) Arguably, pawn goes here too.
Also, you can't sell/buy in the AH without at least a basic addon and expect to make big money.
Finally, I also use some more addons, including TRP3, server hop, NPC Scan, and recount.
How about you?