ACP - Addon Control Panel
BankStack- Sorts/Packs items in bags in a tidy order
Bartender4 - Action Bars
Broker + Plugins - Data Bars
ButtonFacade + Masque - Stylises buttons on action bars
Chatter - Chat Addon
ClassTimer - Keeps track of important timers for in combat
ColorPickerPlus - Easier for picking colors when setting addons up
Bazooka - Used with Broker to display the pluggins
Doom_CooldownPulse - Shows a big icon on screen when an ability comes off cooldown
DragEmAll- Allows you to move the Blizzard Windows.
eAlign - type "/align" ingame to display a grid
Easy World Marker - Type “/ewm” for a tool for assigning world markers.
ErrorMonster - Reduces spam from error messages
Grid - Raid Frames
ImprovedOptionsFrames- Allows you to resize the Blizzard Options, Interface etc. Window.
kgPanels - Panel art in the UI
Leatrix_Plus - Contains a list of very useful settings (type /"ltp" to view them)
nibChatTabs - Stylish tabs on the chat box
OmniCC - Displays cooldown timers over abilties on action bars
Parrot - Combat text Addon
Postal - Mail box Addon for opening all mail at once
Quartz - Cast Bar Addon
Recount - Meter for damage, healing and much more
Reflux - Profile Switching. Works with Mayron's setup. Its safe to disable after setup
ShadowedUnitFrames - Unit Frame Addon
SLDataText - Data text Addon
Simple Power Bar- This adds a bar at the top of the UI for boss special power bars used in some encounters.
TipTac - Tool Tip Addon
Tidy Plates - Name Plates addon
Who Framed Watcher Wabbit - Moves the location of the Quest Tracker
XLoot - Loot frame addon
XLootGroup - Better group loot frame

/ltp - This opens up Leatrix Plus which contains very useful general settings. Worth looking through.
/suf - Settings for the Unit Frames (Shadowed Unit Frames)
/bar - Bartender Settings (Action Bars)
/kgpanels config - Settings for all the graphical art panels being used - Can become very technical.
/rl - Reloads the UI
/classtimer - Settings for the timers on the top of the palyer and target frame - You can remove and add additional tiemrs through this.
/align - Places a Grid over the screen so that you can align UI elements easily.
/dcp - Opens up the Doom Cooldown Pulse Menu - The icon that shows cool downs just below the center of the screen. You will be able to move and resize it and more.
/ewm - EasyWorldMarker - Lets you place World Markers in a Raid if your raid leading for example