There's absolutely no reason to give anyone your PIN. However, even with your PIN, they'd still need your debit card account number, expiration date, and CVC. Then they'd need to encode that onto a card to withdraw money from an ATM. (Your bank account # isn't the same as your debit card #)
Are you sure they're not asking you for your routing number and account number? They can't do DD w/o knowing the routing number
It's possible this is a scam, but even w/ their bank account # and PIN they wouldn't be able to do anything w/o swiping your debit card as well.
edit: it's also possible they're referring to the telephone customer service PIN (which some banks have as an extra security measure to verify your identity. these are (to my knowledge/in my experience) totally separate from your ATM / debit PIN).