Mods

In general I like the idea of a clean, mostly-default UI, but there have been a few mods I've adopted because they make life in the World (of Warcraft) easier.

Yet Another Totem Addon (YATA) - a great mod that incorporates a configurable totem launcher with totem timers. My buttons bars were a mess prior to this.

Omen - the bane of every DPS class, threat. Omen lets you keep an eye on your own threat relative to everyone else in the party.

Quartz - replaces default cast bar and incorporates server lag. Allows you to get spells off a smidge quicker, and every second counts!

Clique - lets you click character portraits to cast spells without losing your current focus. I shift-left-click as Lesser Healing Wave and shift-right-click as Healing Wave. Also control-left and control-right for Cure Poison and Disease, respectively.

Baudmount - equips our shiny new Riding Crop onmount and re-equips DPS-boosting trinkets on dismount. Laziness FTW.

AutoprofitX - sells all gray vendor trash in one click. Handy.

Wowecon - a price database that relies on actual sales rather than scanning the AH for list prices. The only downside is that data is only collected from Wowecon users, so it can be a limited sampling.