Gadfly

"Gadfly" is a term for people who upset the status quo by posing upsetting or novel questions, or attempt to stimulate innovation by proving an irritant. -Wikipedia

gadfly (gad'flī') 1. any of various flies, as a stable fly or warble fly, that bite or annoy domestic animals. 2. a person who persistently annoys or provokes others with criticism, schemes, ideas, demands, requests, etc. -Webster's Encyclopedic Unabridged Dictionary