Punctuation, like all of language, is in flux, and one particular aspect of end punctuation seems to be in the transition stage. I’m talking about multiple marks at the end of a sentence.
Certainly in cartoons and other forms of light reading, and in personal notes it’s not uncommon to see a question mark followed by an exclamation point … or two. However, in fiction such use of end marks is still considered excessive and may even mark an author as an amateur.
The rule, according to the Chicago Manual of Style is as follows:
If a question mark and an exclamation point are both called for, only the mark more appropriate to the context should be retained.
– from 6.123