[arnaudvalette]

! evokes to me the "good move" chess notation, but also the MGS way of telling the player when the AI has spotted Snake.

It eventually leads me to hear the MGS exclamation mark sound when I play or assist to a game of chess and that I spot a good move.

[MalcolmDwyer]

I can't say I remember the associated sound, but the on-screen "!" goes all the way back to the original Metal Gear for NES.

[arrowsmith]

For those who played less PlayStation as a child than I did: MGS = Metal Gear Solid