Miniature Horn of Unity Clicky
Out of all the clickies that you can get during the Everquest Anniversary months, Miniature Horn of Unity is one of the best. This clicky is useful for every class and in basically every situation. The main thing you'll probably be using it for is the mana, health and endurance regen but the damage shield is a nice bonus as well.
The buff that this item puts on you lasts for a total of 36 seconds (6 ticks) so it will regen a total of 1200 HP/MP/END. Not that much in the grand scheme of things but it equals out to be about one spell cast or half a spell class depending on what class/spell you're looking at.