The most famous artificial sweetener, saccharin, was discovered by a grad student named Constantine Fahlberg. He was working with some chemicals in the lab, and neglected to wash his hands properly; when he ate dinner that night, he noticed the bread was unusually sweet and realized it had been contaminated.
Instead of washing vigorously and/or sticking his finger down his throat, he started licking his hands and clothes to double-check his hypothesis and then tested the chemicals in the lab-and when we say "tested" we mean he licked them, too.
"You see that? I licked the shit out of that. For science."
Meanwhile, Jim Schlatter took it up another notch when he discovered aspartame (chief ingredient of Equal and NutraSweet). Schlatter had a habit of licking his fingers while reading, an absolutely terrible habit considering he had to both handle chemicals and lab reports regularly. Thankfully, when the inevitable happened, all he experienced was an annoyingly sweet taste instead of a horrible death by poison.
"I probably shouldn't eat this. Oh, well. Science."