Emoticon
A face made of punctuation and read with your head tilted — the smallest and most widespread form of ASCII art.
On 19 September 1982 computer scientist Scott Fahlman suggested on Carnegie Mellon's online bulletin board that jokes be marked with :-) and serious posts with :-(, after a tongue-in-cheek thread about mercury spilled in a lift had been taken literally. The idea travelled over ARPANET and Usenet and quickly sprouted hundreds of variants: winks, glasses, moustaches.
The point was practical. Plain text has no tone of voice, and a tiny sideways face was enough to tell a joke from an insult. When chat clients and phones later began swapping the characters for pictures, the successor became emoji — but the three characters still work on every terminal ever built, which no emoji can claim.