Election-night pundits talked a lot about how this presidential election was unique, and it certainly was surprising in many ways. But Trump, the candidate, was as different from previous presidential candidates as the election itself was from previous elections; not just in his demeanour, but in a host of measurable ways. (All of the following assume he actually takes office in 2 1/2 months, which seems likely but I feel like I need to cover myself in case some unlikely event prevents him from doing so.)
Trump will not be the oldest president to take the inaugural oath, but he will be the oldest to take it for the first time (he is 70, Reagan was 69). Reagan also beat Trump to become the first divorcé to be president, but Trump has two divorces to Reagan's one. He is the first billionaire to be elected. Ironically, however, Hillary Clinton raised twice as much money as Trump did. This makes him the first person to win an election in spite of raising less than his opponent since...Bill Clinton did it in 1996. (I was not aware of this history, but the fact that Trump had raised so little money made me think he had little chance, I guess in part because I assumed that meant little enthusiasm for his candidacy.)
Trump scored basically no major newspaper endorsements, which is truly remarkable in some respects. A list at wikipedia shows that, among the few papers to endorse him, the best known was the National Enquirer. He was also endorsed by papers in Jacksonville, Las Vegas, and Hillsboro (OH). This is probably the first time a president has been elected without being endorsed by a major newspaper, although if you define a newspaper by its circulation, the Enquirer is probably bigger than almost any of the regular dailies.
I think the biggest thing that makes Trump different from his predecessors, certainly one that stands out, is that he has no previous political or military experience. Every previous president has had at least one of the two, often both. Relatively few military leaders have been elected without previous political office, among them Ulysses Grant and Dwight Eisenhower. Prior to Trump, the president with the least experience was almost certainly Barack Obama, who had been a U.S. Senator for only 4 years, although he had been in the Illinois legislature for 7 years prior to that. I have wondered before (and I thought I wrote about it, although I can't find it right now) how Trump's candidacy would affect future elections. If he lost, of course, odds are that we would not see another outsider like him for many years. I suspect that the machinery of the Republican Party has been moving since the primary season started to prevent the possibility of its recurrence, and I doubt they will want to change just because he won.
But since he has won...what then? Are we going to enter into an era of outsider presidents? Will well-known actors, singers, and athletes compete for the highest office, and will major parties welcome them because they have huge name recognition, loyal fans, and the virtue of not being part of the Washington establishment? I have heard sportswriters joke about how such-and-such an athlete could win the governorship of his home state. This was not really such a stretch, as Jesse Ventura and Arnold Schwarzenegger showed, and Al Franken won a Senate seat with no political background outside of political humour. But that seems like a small thing to aim for now. Could Stephon Marbury or Cam Newton run for president now that Donald Trump has paved the way?