I randomly get a strong urge to howl at the moon whenever I see it. I usually act on it, and freak out whatever friend I happend to be walking/driving/sitting with.
Also have the occasional urge to mutilate people in a very systematic and cold-blooded manner, usually involving a sharp knife, and fire. Buuut then, who doesn't, right? ^w^
Then there's the random urge to get up and walk out of class while the professor is lecturing, or the urge to turn and start drawing on the nearest surface, be it paper, desk, wall, or person.