No, it actually is not the barf emoji… according to Apple, the ”tears of joy” is the most often used emoji (I remember when they were called emoticons) on iPhones. Red heart takes second place, with crying landing third. According to the survey, tears of joy are particulary popular in the UK and US.
On a side note, Unicode, an organization that sets down the global emoji standards, seriously considers getting rid of the poop emoji on the ground of it being in bad taste.
No shit.