WTF is an interesting case because it can express both versions. WTF?! with an emphasis on the question means you lack information about the subject, WTF!? wit

WTF is an interesting case because it can express both versions. WTF?! with an emphasis on the question means you lack information about the subject, WTF!? with an emphasis on the exclamation means you know what occurred but you're expressing shock/outrage. E.g. the first version is "I don't know what just happened" and the second is "I can't believe what just happened". With an interrobang there's no way of expressing both versions.