WowAce

A fancy LDB reputation display, show faction reputation and reputation change history

Adirelle's unit frames, based on haste's oUF.

Tooltip of awesomeness. Moo. It'll graze your pasture.

Displays Instance Maps

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

Track all threat redirection ability transfers and cooldowns (Misdirection and Tricks of the Trade).

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

Show the transmog appearance of an item when you mouse over it, and shows collection-status in bags, shops, and elsewhere. Works on transmog, mounts, pets, and decor.

Cryolysis 2

Questing minion

Test whether the player can really dispell a buff or debuff, given its talents.

Keeps track of your current location.

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

Displays online guild mates.

Keeps track of your top hits, heals, criticals, etc.

XRS

Antagonist

Incoming Heals

Adds a status to Grid for debuffs applied by Raid Bosses.

Keeps track of HoTs, DoTs, Buffs and Cooldowns. With audio and text alerts to refresh them.