Apple unilaterally decided that the pistol emoji actually refers to a water pistol. Most other vendors followed suit a year or two later. IMO this was an incredibly stupid thing to do. Someone on iOS could text their classmate something innocuous like "Can't wait for the school's field trip to the water park tomorrow!<gun emoji>". If the recipient was also on iOS, they'd see a squirt gun. If the classmate was on Android, they'd get a very different impression.

Side note, does HN not support non-ASCII characters? It looks like the actual emoji was stripped from my comment