Robert De Niro
The history: The year was 2011. Donald Trump had been hitting the birther beat especially hard. Bobby De Niro was doing an interview with Brian Williams in the middle of the Tribeca Film Festival, and made some not-so-subtle comments about it. "I won't mention names, but there are certain people on the news in the last couple of weeks -- what they're doing is crazy," he said. "They're making statements about people that they don't even back up. Go get the facts before you start saying things about people." When Williams asked if the person had a show on his network on Sunday night (i.e., Celebrity Apprentice), De Niro said yes, and compared the "mysterious" person to a pathetic car salesman. In a subsequent interview with Fox & Friends, Trump basically called De Niro stupid.
Have they made up? Not really, but do either of these guys care? That'd be a hard no.
The history: In 2004, Trump sent Cuban a super-condescending letter of condolence over his cancelled show, The Benefactor. He also went after him in his 2007 book Think Big. But things really heated up in 2012, when Cuban attempted to challenge Trump in the name of charity. If the living hairpiece shaved his head, the Mavs owner would donate $1 million to charity. Rather than do that, Trump decided to mock Cuban's net worth and current show (Shark Tank). They scuffled for a bit. Later in 2013, Trump said he was better-looking than "dopey Mark Cuban," which, dude, pick your battles.
Have they made up? Oddly, yes. Last month, Cuban called Trump "probably the best thing to happen to politics in a long, long time," and so far, it actually appears to be sincere. Go figure.