Carl Scheele was an 18th century chemist who had some amazing accomplishments. He discovered oxygen, for instance. He also isolated and identified a slew of other elements, including molybdenum, tungsten, barium, hydrogen, and chlorine, plus a bunch of organic acids. But almost 300 years later, Scheele's name is known best for a pigment he developed called Scheele's Green, which became quite popular, especially in wallpaper. It was loaded with arsenic, however, which was released into the air when fungus consumed the wallpaper.
Scheele himself had a habit of studying his elements and compounds by sniffing them and tasting them, and ended up furthering our knowledge of how dangerous these chemicals can be. When he died at age 43, the cause of death was determined to be mercury poisoning. It probably didn't help that he had, over time, consumed a fair amount of arsenic, chlorine, and other heavy metals along the way. Scheele is only one of five scientists whose work ended up either killing them or making their lives miserable, tragically chronicled at Cracked.
Update: To be fair, Cracked's list could be described as "four scientists who brought destruction upon themselves, and one who brought destruction on everyone." However, Geoduck pointed out that the fifth, Thomas Midgley, was indeed killed by his own invention. Thanks, Geoduck!