Exclamation Mark is the name given to the punctuation mark of '!'. It is often used at the end of a sentence, replacing a period in order to show alarm or surprise. In written text, it is most often used in dialogue and rarely during prose.
Between its creation during the 1400s in Britain and the 1600s, it was known as the 'note of admiration'. Ever since then it has been commonplace in the English language and has been known as the exclamation mark. It wasn't until the 1970s that the Exclamation Mark made its way onto typewriters. Before that point, one had to type a period, hit backspace and then type in an apostrophe.
In video games, exclamation marks are, for the most part, used as any other appropriate punctuation is used (and should therefore not be added to this page, to avoid every video game with text being added). Perhaps the most notable exception is in the Metal Gear Solid franchise. In MGS 1-5 (as well as all subsequent spin-offs) an exclamation mark above the enemies head showed that the enemy had been alerted. This became a source of inspiration for many MGS-based parodies.