The interrobang, also known as the interabang, is a nonstandard punctuation mark used in various written languages and intended to combine the functions of the question mark (also called the “interrogative point”) and the exclamation mark or exclamation point (known in printers’ and programmers’ jargon as the “bang”). The glyph is a superimposition of these two marks.
Chief Judge Frank H. Easterbrook of the United States Court of Appeals for the Seventh Circuit, in his opinion in the case of Robert F. Booth Trust v. Crowley (No. 10-3285), used an interrobang on page 8, at the end of line 10.
You can find the entire opinion here.