My favorite clowns:   

complete the organizer - check yes on sold real estate but send no documents.  Most say not sure what I needed..... duh! maybe a phone call would have cleared that up BEFORE you brought me your paperwork. 

Child born in 2022 - no social security number provided   no explanation why not    Have to waste my time calling to get the answer

Client that turned in Estimated tax payment worksheet with check number/date missing for one payment AND that voucher attached.    However, totally positive they made that payment.