My favorite accidental discovery: "It was initially studied for use in hypertension and angina pectoris. The first clinical trials were conducted in Morriston

My favorite accidental discovery: "It was initially studied for use in hypertension and angina pectoris. The first clinical trials were conducted in Morriston Hospital in Swansea. Phase I clinical trials under the direction of Ian Osterloh suggested that the drug had little effect on angina, but that it could induce marked penile erections." Had someone not been paying close attention, Viagra would have died at phase I.