Many characters keep a piece of skin at the top of the chest exposed to the elements by a v shaped clothing design. Oftentimes even if otherwise the person is reasonably dressed or wheres armor everywhere else. This serves to show some Fanservice without being overly racy about it. Males usually have it to show some laidback tendencies, females do it for any real reason.
Mystique does the unzipped up variant in First Class. Little odd as the outfit is supposed to stop bullets.
In Assassin's Creed
Lucy has this in the first game. Atfirst it looks like fanservice but a closer look and it resembles the assassins emblem.
In Lost Planet
Luka has one despite the planet being nearly covered in ice. She atleast puts on an undershirt when it gets worse.