1800
Back then, the electors used the original procedure. The electors had two votes each, the President was whoever got the most, and the Vice President the second most.
Thomas Jefferson and Aaron Burr were tied for electoral votes, and the election then went to the House. The Reps were TJ 8, AB 6, divided 2 for 35 votes until one Rep decided to have no vote instead of AB. That made the final vote TJ 10, AB 4, none 2, and TJ got elected.
1824
Though Andrew Jackson got the most electoral votes, he did not get a majority, and the election went to the House again.
House Speaker Henry Clay detested AJ, saying of him "I cannot believe that killing 2,500 Englishmen at New Orleans qualifies for the various, difficult, and complicated duties of the Chief Magistracy." He leaned on state delegations to vote for his preferred candidate, John Quincy Adams, and JQA won.
1876
That was a very close and contentious election, with a lot of disputed results. This produced a constitutional crisis, and Congress resolved it with a 15-member Electoral Commission. Democrats accepted Republican Rutherford Hayes as President in exchange for concessions like the end of the remaining Federal occupation of Southern states.
1960
Illinois voted for JFK over Richard Nixon with a very narrow margin, with some Republicans claiming that Democrats stole the election for JFK there.
2000
The Supreme Court decided Florida for Republican George Bush II, a state where he had a very narrow margin of victory.