My addon list is full of Lesser Known Addons:
TradeSkill Bookmarks: This small addon adds a bookmark button to the top of the tradeskill frame so you can quickly return to those recipes later.
WordMap Player Dot Resizer: Resizes group and raid player dots on the WordMap.
QuestMapWithDetails: see quest details and quest list at the same time.
Juwe: shows Gem Stats instead of Names
stAddonManager: Addon Manager with profils
Basic Threat Bar: Too many use Omen but all you need to see in Threat is this small bar.
Item Link Macros: allows you to add item links into your macros simply by Shift-Clicking an item link while the macro window is open
DerangementPetBattleCooldowns: expands the default Blizzard Pet Battle interface to show the cooldowns, and buff/debuff durations for all abilities in a pet battle, including your enemy's and even benched pets.