Rule: I can't convince you never to use Comic Sans, but DO NOT ever, EVER use it on your resume or cover letter. I don't care how "fun" you are or want to seem. This is not the place. Don't do it. I will go to your parents' house, pose your childhood toys in offensive positions, set fire to the whole thing, then photoshop your face on a picture of your parents having nasty sex and send it to you and all your friends. It is at that point that I will come find you and punch you straight in the reproductive organs, step over your groaning face, open up your email, and attach that picture to an email to your girlfriend/boyfriend asking if we can "try this next time."
Don't do it.