Lightbulb

The lightbulb is an icon that appears over your head when you meet the conditions to aquire certain important quests. These are usually event-related or class-related quests. You can double-click the lightbulb to receive the quest right away instead of talking to the person who gives the quest. You can still go to the specific NPC if you want, but clicking the lightbulb is just like clicking the actual NPC.