WowAce

Allows the user to preview and track their progress in the collection of various transmogrification appearance sets

Libra

Show all the leyline taps in Suramar

Checks your gear before bosses and yells at you if you're an idiot

GrindStatus

XRS

Automated smart raid marking to speed up trash clearing in instance runs

Inspects all members of raid and saves in database, as well as lists people's dkp values

Configure triggers to send messages to your raid team such as timers, rotations, and health/power based triggers. Raid smarter not harder.

CandyBar style cooldown display

Try on different gear and see their total stats and their differences. In short, an ingame CT-Profiles-like addon.

Switch macro depending on zones or BigWigs boss modules.

Makes a sound when your focus starts casting. Use with [target=focus] macros for interrupts (Counterspell, Spell Lock, Wind ...

Reports in raid chat whenever a raid member "fails." /EnsidiaFails to configure.

Wowhead Data dump for GatherMate

HUD that you can tweak the way you want.

Reduces interface tedium by doing the little things for you.

LibItemInfo-1.0

Tooltip scanning library.

Regain that wasted space!