ADHD (3.5e Trait)
From D&D Wiki
You're bright, unusually so, but you're so easily — HEY LOOK A NICKEL
Benefit: you gain a +2 to any knowledge skill.
Drawback: the bad part is you cant stay focused for long; you get a -2 on spot, listen, concentration and any other skill requiring a high degree of concentration (higher or lower at DM's discretion though if the positives are higher there should be a corresponding increase). You are also required to make a concentration check when attempting to do anything (outside of battle) that requires patience, long periods of inactivity, long periods of paying attention, or similar (for the purposes of this article half an hour is a long period of time). If you fail, your character becomes disinterested and goes off to find something more fun to do... they also may be distracted by something particularly interesting, the character must make a Will save (determined by DM and how interesting the afore mentioned item, event, person, etc. is) to see if they go off and investigate or stay on task.
Roleplaying Ideas: Your character may seem childish or be distracted easily off of important quest related topics. They may also be distracted b— OH MY GOD WHAT THE HELL IS THAT SHINY THING. They are rather creative and can use what they know in ways you probably don't expect "hey you think I can use woodshape/stone shape to make razor wire connecting all the trees/columns/buildings together at various heights?"