Mouseover Action Settings - provides mouseover ability for action bars and micromenu.

Clean Icons - Mechagnome Edition - replaces the default Icons with a better look.

HideActionBarBorders - hides the button borders so I can use Clean Icons.

LiteButtonAuras - Shows your buffs on you and your debuffs on your target inside your action buttons with a colored border and timer.

tullaRange - Allows the user to make action buttons change color when an action is out of range or is out of energy/mana/focus/etc.

Clean Icons - Mechagnome Edition - Replaces the default game icons to change the look without using a mod.

Micro Menu Recolor - Changes the color of the micro menu buttons.

SharedMedia - Inserts media(textures, bars, borders, etc) into LibSharedMedia's storage. They can then be selected by any addon that supports LibSharedMedia, a lot of them do. I have collected many various fonts and statusbar textures which I insert into SharedMedia for my UI.

Auctionator - Designed for casual everyday auction house users. Auctionator makes the auction house easier to use by presenting auction house listings clearly and succinctly and by eliminating the tedium involved in posting and managing auctions.

AdiBags - Displays your inventory in one bag broken into several sections using smart filters. It requires no setup but you can create your own custom filters.

WeakAuras - Allows the display of customizable graphics to indicate buffs, debuffs, and other relevant information.
This addon has a learning curve so it may not be good for a casual player | WoWHead Guide

Anti_Spam - Addon with a simple UI to filter your chat by adding keywords or character name.

devnull - When you enter a capital city it will ignore people who /yell. It will ignore spammy NPCs (ie. Ironforge bread vendor, Topper McNab in Stormwind etc). It will ignore duel spam (A has defeated B in a duel). It will ignore emotes except those directed at yourself. It will ignore drunk spam (X looks tipsy). It will ignore tradeskill spam.

Notifly - Plays a sound when you get a whisper from other players.

Prat - a chat enhancement addon made up of modules which can be enabled that provide additional functionality. You can format how players names look in chat including their class color and level. There is an alt module that scans your guild log to find players alts, it then adds their main name in chat in parens after their current character name. It provides the ability to bind keys to chat channels, I hit G to type in guild chat.

I use Proxima Nova as my main UI font, Proxima Nova Condensed for chat and Lemon Milk for Nameplates.

Drift - Modifies default UI frames so you can click and drag to move and scale. Left-click and drag anywhere to move a frame. Right-click and drag up or down to scale a frame. Position and scale for each frame are saved.

Simple Item Levels - Show item levels on: The character panel, The inspect panel, Weapons, armor, and artifact relics in bags. Shows missing enchants and gems on character panel.

ItemRack - a mod to make swapping equipment easier through popout slot menus, equip slot buttons, gear sets and automated swaps. This is great for a class that has multiple sets of gear like a warrior that can either tank or dps.

Clique - Simple addon that enables click-casting and hover-casting on your unit frames and in the game world. You can bind virtually any mouse or keyboard combination to a spell or macro. In it's normal configuration this enables you to use the bindings over your unit frames in order to cast spells directly on that unit. This allows you to more quickly select both the spell to cast, and the target of the spell without requiring an extra click.

Bazooka - Adds information bars on the top or bottom of the screen which provide data broker plugin support.

Broker Everything - A collection of modules to display various information ingame about the game, your character, friends, guild and many many more.

BagSync - tracks the items on your characters and displays the information in collective tooltips. You can see BagSync highlighted in red in the screenshot. Mavrock has 6 Healing Potions, 5 in bags and 1 in bank. Vranx has 5 in bags.

LS: Toasts - Replacement for the default alert system. Better toasts.

Gnomish Inbox Shrinker - Replaces the default inbox UI with a minimalistic, scrolling list that gives you a much better overview and no paging.

Postal - Offers enhanced mailbox support by providing many features.

MinimapLine - Draws a line from the player arrow to the edge of the minimap to make your direction more visible.

HandyNotes - Notes for your maps. A lot of Plugins available.

Leatrix Maps - Adds enhancements to the World Map.

TomTom - Your personal navigation assistant in World of Warcraft. This addon is very simple, but provides a nice set of functionality.A draggable coordinate display showing hundreth precision, this frame can be hidden or locked. WorldMap display of player and cursor coordinates, these displays can be hidden. The ability to set waypoints based on coordinates.

World Map Tracking Enhanced - Provides enhanced features to WorldMap's Tracking Options. Replaces the built-in tracking option dropdown and allows you to further toggle the displaying of the most popular WorldMap enhanced addons such as HandyNotes and GatherMate2.

Leatrix Plus - A collection of fixes for things in Wow. Automation - automate quests, automate gossip, accept summon, accept resurrect, release in PvP, auto sell junk,auto repair. Social - block duels, block party invites, block friend requests, auto party from friends, invite from whispers. Plus many options for Chat, Text, Interface, Frames and System changes.

TinyPad - Simple but powerful notepad addon that's easy to use.

Threat Plates - Addon for customizing your nameplates. It offers a high amount of customization and tweaks to how your nameplates react and look.

GTFO - Provides an audible alert when you're standing in something you're not supposed to be standing in. In some cases, you'll be warned before you start taking damage. It's particularly useful for individuals that play with their spell graphics turned down or for those that just need a little extra help being told to GTFO. It also helps out with PvP when you can't tell who's casting the AOE.

BattleGroundEnemies - A lightweight Addon to show you all enemies, allies and important player-specific information in a battleground.

Capping - A battleground timer mod with some extras. Current Features: Start Timers, Node Timers, Flag Respawn Timer, Flag Carrier Display with health percent. Port expiration timers/Queue wait timers/Scoreboard repositioning/Capture bar repositioning.

Classic Quest Log - Restores the old quest log with the familiar list of quests on the left and details on the right.

Quester - Enhances the questing experience by improving upon the built-in Quest UI, smoothing some rough edges and providing a few enhancements. Quest levels in the quest log, on the map, in the quest tracker, in NPC dialogs, everywhere! Difficulty coloring of quests, Progress coloring red -> green of objectives in the quest tracker(I have manually disabled this), Quest progress sounds: "More work?!" when an objective is completed and "Job's Done!" if the quest is complete.

QuestClicks - Creates clickable buttons for usable quest items. Also creates buttons for Tradeskill Items, Quest Starters, Toys and Pets, Garrison Rewards, Recipes, Lootable Containers.

ZaremTooltip - A simple and lightweight addon that enhances your Tooltip.

FrameColor - Lets you customize the color of Unit Frames(HUD Elements), Action Bars and Windows within the Default UI.

Compact Vendor - Converts your vendor frame into a compact scrollable list with a search box.