Coffee.
Also really overlooked as a psychoactive substance. Drink a cup and your instantly in a better mood , and ideas fly better , and your brain becomes twice as functional for about an hour.
Oh , and it tastes and smells great , and makes you feel more important than you actually are.
http://www.erowid.org/chemicals/caffeine/caffeine.shtml
^^^ Lots of drug geek stuff on it their.