As I'm sure you know, there are two types of "What?" in the world. The first type simply means "Excuse me, I didn't hear you. Could you please repeat yourself?" The second type is a little trickier. It means something more along the lines of "Excuse me, I did hear you, but I can't believe that's really what you meant.
Lemony Snicket, The Austere Academy
humor, language