Saccharin - Constantin Fahlberg and Ira Remsen

After spending the day studying coal tar derivatives, Fahlberg left his laboratory and went to dinner. Something he ate tasted particularly sweet, which he traced to a chemical compound he'd spilled on his hand. Best of all, it turned out to be calorie-free. He cut Remsen and the university out of millions of dollars when he secretly patented Saccharin.