WowAce

World of Warcraft Classic addon to display current zone information.

LibMobHealth-4.0

ControlFreak

LDB display of the players current damage percent modifier

With Mists of Pandaria Blizzard publish all characters from an account unless you disable that 'feature'. This addon warns you.

Nostalgia

Mage Portal Whisper: whisper custom message when someone asked for a portal but youre busy.

Automatically calls ForecQuit() right before you are AFK-disconnected to quit wow instead of going to the character selection...

ManaMeter2

FailBotSpam

Gnomish Top100 GUID Catcher Xtrem

Auto-target your Prospector/Milling/Enchanting skills. v1.18

Adds the "pixel perfect" font "Visitor" to LibSharedMedia

Blocks all whispers except from people in your guild and friends list.

Auto sizes frame layout depending on group/raid size

phLayoutLib

Shows on the minimap where to fetch Finklestein's reagents

Automatic switching to FFA loot for Mimiron phase 3

A database of poeple wo can craft your items

Library to handle and store information about frame that are possible targets to anchor other frames to.