If you're a fan of GTA Online and/or have been watching this space lately, you'll recognize the Deluxo, which takes after the famous flying DeLorean from Back to the Future and is available via Doomsday Heist's DLC.
As you can see in this short montage put together by IGN, you can drive the Deluxo, you can hover with it just above the road, or you can go flying as you would in any aircraft available in the game.
In case you're thinking that a flying car is in no way better than a plane or a helicopter, consider that landing a helicopter in GTA requires a bit of maneuvering around, while planes need an airstrip (ideally) and, of course, you have to stick the landing.
So being able to take off and land seamlessly using a car is definitely the most efficient way of getting from A to B while playing the game. And to make things more interesting, the Deluxo is equipped with missiles, so it's got offensive capabilities, too - although there are no scenes showing it doubling as a submarine, which it is supposedly able to do.
The only thing it doesn't do, unfortunately, is go back in time like the movies' DeLorean, which could come in handy while playing an action-packed video game like Grand Theft Auto.