Aaron Burr
The nation's third vice president had his strengths: he has been hailed as "one of the best presiding officers the Senate has ever seen." Unfortunately, his political gifts were dwarfed by his role in two of the biggest scandals ever to strike the office. In an 1804 duel in Weehawken, N.J., Burr shot and killed former Treasury Secretary Alexander Hamilton, a Founding Father and Federalist Papers author held in sufficiently high regard that his image graces the $10 bill. That episode torpedoed Burr's career — he was indicted for murder and fled to the South — but the former lawyer wasn't done making mischief. In 1807, he was charged with treason for allegedly masterminding a plot to attack the Spanish colony of Mexico; some claimed he also planned to liberate the Union's Western states in order to form his own empire. At his trial, Burr subpoenaed President Thomas Jefferson, who — in an early example of executive privilege — refused to testify. Burr was later acquitted.
—Alex Altman