Interrobang (noun, also known as interabang)
I’m going to defer to Wikipedia on this one but this is essentially the combination of ?! at the end of a sentence to indicate shock or incredulity when asking a rhetorical question. As in: How much do we owe on our credit card?!
If you follow the Wikipedia link you’ll see the correct way represent this little known punctuation tool is to type one character over the other … but find me a computer keyboard that will cope that with that with a minimum of stress. On a typewriter, maybe.
While we’re on obscure punctuation marks, I’m impressed by the Frenchman who suggested the Irony Mark (aka Snark), Doubt Point, Indignation Point, Love Point and several more. You’ve got to like that thinking.
Thanks to the erudite King of Quirk, Lliam, for this tip-off.