Eigenpoll : Cognitive improvement : Levodopa

L-DOPA is the precursor to the neurotransmitters dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline) collectively known as catecholamines.
Seems to increase creativity.

http://en.wikipedia.org/wiki/L-DOPA
http://bigthink.com/ideafeed/science-stumbles-onto-a-creativity-pill