Gaming has characters with memorable personalities. But Master Chief, the protagonist of the Halo series, is a total void. And there's a reason for that.
According to the studio's lead writer Joseph Staten, "We left-out details to increase immersion; the less players knew about the Chief, we believed, the more they would feel like the Chief."
This doesn't mean the character is boring, because that would imply he has his own personality. Rather, his personality is dependent on the player's, as Master Chief follows the events as they unfold in the game.
The Chief is one in a long line of silent gaming protagonists who are designed to make players feel like the character — and like a badass. "Immersion was the main goal here," adds Staten. "Also keeping the Chief a man of few words reinforced what we wanted to be a tough-as-nails soldierly persona."
Since Master Chief is not fleshed out in the games (allowing players to do that!), this lack of explicit characterization caused roadblocks during the development of the proposed Halo flick. In fact, at one time during the since shuttered production, Master Chief was going to be relegated to a "supporting character".