His name is Noctis, but in game, he's typically called 'Noct.' In the scene in the promo trailer, Stella calls him by his full name.
game movie trailers are less game trailers and more movie trailers. So, the new Final Fantasy Versus XIII trailer wouldn't seem that different. It is! According to the game's director, Tetsuya Nomura, the trailer features at least one scene rendered in the PS3 in real time. The scene is where main hero Noctis meets blonde-haired heroine Stella. If that wasn't enough (it never is), the main character uses a shortened nickname of his moniker which means "of the night". Says Nomura:
Well, dur. You can't just start off calling him "Noct." Gotta work up to that. And if you get really tight with the guy, maybe, just maybe you can call him "Nocty". スクウェア･エニックスブース 一般公開に合わせて、クローズドメガシアターの観どころ教えます！ [Famitsu]