1792 - Highwayman Nicolas J. Pelletier becomes the first person executed by guillotine.
Quite the historical distinction for old Nick. It must be pointed out however that he wasn't the first person who ever had his head lopped off as a punishment, just the first lopped off by this particular device, which I know your dying to learn more about:
The device derives its name from Dr. Joseph-Ignace Guillotin, a French physician and member of the Revolutionary National Assembly, on whose suggestion it was introduced.
The basis for his recommendation is believed to have been his perception that it was a humane form of execution, contrasting with the methods used in pre-revolutionary, ancien régime (old regime) France. In France, before the guillotine, members of the nobility were beheaded with a sword or axe, while commoners were usually hanged, a form of death that could take minutes or longer - other more gruesome methods of executions were also used, such as the wheel, burning at the stake, etc.
In the case of decapitation, it also sometimes took repeated blows to sever the head completely. The condemned or the family of the condemned would sometimes pay the executioner to ensure that the blade was sharp in order to provide for a quick and relatively painless death.
This does seem rather more humane. Cruel and unusual for me would be being forced to sit through repeated viewings of An Inconvenient Truth and incurring brain-death. I would probably be paying off the executioners as well---just lop my head off now and put me out of my misery.