It’s not often you witness the birth of a new punctuation mark, but this could be it. The SarcMark:
US company, Sarcasm, designed it and is selling it for $1.99.
Their media release says, “Statements have the period. Questions have the question mark. Exclamations have the exclamation mark. When you see the newest punctuation mark for sarcasm, you’ll know the writer of that sentence doesn’t literally mean what they’re writing; they’re being sarcastic.”