is an interrobang. It marks the end of a sentence that's both a question and an exclamation.
Interrobangs aren't used much, nowadays, firstly because almost no one has a computer with an interrobang key on it, and secondly because there's really nothing difficult, complicated or disreputable* about writing ?!
It's a pity, in a way, because that interrobang is really rather a lovely thing to look at.
Thing That'll Just Confuse Everyone If You Use It Today: an interrobang. The interrobang was invented by Martin K Speckter in 1962, and suggested names for the sign have included exclarative, which I find much more lovely and convincing than interrobang. The interrobang was most used during the 1960s, when some typewriters even featured an interrobang key.
There's also an inverted (upside down and back to front) interrobang for marking the beginning of questions in Spanish languages.
This is sometimes rather pleasingly called a gnaborretni.
*Having said that, there are those who thoroughly despise anyone who uses either ?! or !? (the second order of the punctuation marks is the less usual). Still, those people generally despise the interrobang, too. I suppose all we can do is either restrict ourselves to the single question mark, or be generous and let people have their fun.