Dr. Barry J. Marshall was convinced that H. pylori bacteria causes stomach ulcers, but no one believed him. Since it was illegal to test his theory on humans, he drank the bacteria himself, developed ulcers within days, treated them with antibiotics, and went on to win a Nobel Prize.
Semen doubles as invisible ink. During WW1, a member of British intelligence M16 discovered that semen won't react to main methods of detection. The agent thought he'd solve a great problem, but had to be removed from his department after becoming the butt of too many jokes
Source: awesomeinventions.com
Source: awesomeinventions.com