Our 'PINS' for bank/debit/credit cards are six digits not four. The six digits work in the UK too, at POS machines/ATMs. Not sure why the UK went with four when (obviously) they can cope with six.
I use my service date with a previous employer. Memorised it years ago since I needed it requesting ID tickets. Since it was already there, nobody could guess it, nobody could track it down (airline went out of business 20+ years ago). I also cover my hand when keying it in.
Not 100% safe, but better than 1234!