AddOns. They seem to be a main staple in WoW these days. Back in '07 when I started, I think Cartographer and QuestHelper were the only two I had even heard of. Now, there are thousands. I have a select few I cannot live without:
How about you? Are you an Addon-ict, an addon casual, or are you living addon free?DBM - For those pesky boss encounters
Postal - So I can check all my mail automatically. Comes in handy with as much stuff as I sell.
SellJunk - I love selling all my grey junk in one shot. Comes in handy after a day of Archaeology.
NPCScan - Gotta find those rares
Pet Tracker - Lets me know what pets are available by zone, and where. If there is an icon on my world map, I don't have that pet in my collection.
ZygorGuide - Got this YEARS ago after I heard about Quest Helper, but wanted something more in depth.