So everyone is talking about those Greek sign pranks right? But I got something just as bad (I haven't used it as a prank but I've just encountered it on my own -> pranked my self)

So on Mac OS you can type this character with ALT+Space and it looks like a space, but it isn't. If you don't have render whitespaces on you would never know that it is not a space... Imagine the time you can spend on finding that xD you mistyped 1character and BAM broken xD