The only unofficial code I can think of is when one of us has another family member with us, we'll use our DSN followed by "plus 1, 2, 3, 4, etc." to tell the other ones how many people are with us. Nothing fancy, but that'* used every once in awhile.
As for the "10-98" code, we use that alot because every Monday morning at 1AM we press a button that sets off a jailbreak alarm. We do that as a test once a week to make sure it'* working. That'* the only reason we use it so often.