Modular Monday - OPie

Today we've got a surprisingly light-weight mod with a lot of functionality, especially class to class. OPie is a tool that aims to save you space on your action bars. It's kind of hard to describe, but the video above gives you a pretty good visualization and a basic idea: set up hot keys in order to make ring-like menus pop up (basic or animated) at your whim. Like PowerAuras, a lot of the specialization and customization comes based on the class you play. All classes can use it as a cool way of managing your mounts, pets and trade skills for example, but here are a few cool uses for each class specifically

Paladins - Easy way to manage your auras blessings and seals

Mages - A godsend for keeping all your portals and teleports on a few buttons.

Warlocks - Great for keeping all your pets on one button, as well as soul and spellstones

Druids - All your forms at your fingertips

Hunters - Aspects on the fly, pet commands whenever you need

Death Knights - Easy presence swaps, ghoul commands and various cooldowns

Warriors - Stance swapping for all you dancers out there

Rogue - Stealth, Vanish or Shadow Dance, poison management, and stuns plus crowd control on one key

Priests - All your raid buffs on a ring, and quirky spells like Mind Control or Mind Soothe

Shaman - Can be used in conjunction with your new call totem spells, plus a great way to manage weapon imbues

I'm sure there are a ton more out there. The default rings on the mod include things like trade professions, raid markings, mini-map trackers, and other class specific rings. It's super customizable and I highly recommend you give it a shot.