Called the 'SarcMark', it has been designed by an American firm to indicate sarcasm. Check out the ad below:
As this article in the Telegraph points out, without the benefit of tone of voice, expression sarcasm in print can be fraught with risk. But alas, we now have something which will make explicit that which may have been intended to be subtle!
I'm just itching with ideas about how I can teach this new one to my students! Free download here.
(Hat tip: Kathryn EDEM629 for this!)