Can I use several question marks when a character is confused? Or that little mark with a question mark and an exclamation mark when a character shouts a question?

As a general rule of thumb, try to choose one end punctuation mark for a sentence. A string of question marks won’t capture your character’s confusion as well as a carefully chosen gesture, action, or line of dialogue.

That combination of a question mark and an exclamation mark is called an interrobang (or interabang) and it is actually a question mark superimposed on an exclamation mark. It can be used when a question is exclaimed. But before you put it to use, consider this: is a punctuation mark really the most effective way to communicate the character’s emotion? More often than not, you’ll likely serve your fiction best by choosing the exclamation point or the question mark. And you’ll accomplish even more if you focus on description, action or gesture to reveal the nuances of the character’s experience.

Also, consider the connotations that come with multiple punctuation marks at the end of a sentence and how well those interact with your intentions. Some put the interrobang in the same category as the emoticon. Are you looking for that feel in your narrative?