Bloody Mary

Bloody Mary is a ghost who supposedly is summoned after someone speaks her name three times in front of a mirror in a completely dark room. The most common interpretation of the legend goes that Mary Worth is the spirit of a young mother whose baby was stolen from her and subsequently goes crazy with grief, ultimately killing herself. 

Summoning Bloody Mary is popular as a game or a dare, because supposedly after she comes around, she proceeds to attack the summoner—often ripping off their face or gouging out their eyeballs—aiming to drive them insane or to an early death. And, if you don’t die after summoning her, then she will haunt you for the rest of your life. So, not exactly a great scene in any scenario.

Source: buzzfeed.com