Clickies are items with an effect that is triggered by right-clicking the item. All clicky items must either be clicked from an inventory slot (not inside a container, pre-VoA; with VoA expansion, such items can be clicked from inside a container) or from it's appropriate equipment slot. Clickies with the same recast type share the cool down timer, so if a clicky with a recast type 1 is clicked, then none of the clickies with a recast type 1 will be clickable until the clicked item has cooled down.
Just like spells, there is a wide variety of clickies available. Some can be used for trash buffs, some for looks (illusions) and visual effects (particles), some for buffs, some for debuffs, and some only for use in quests. The following pages are for unlimited charge clickies: