I always get my Dad Darrel Lea or Charlesworth Nuts stuff. Only because Mum doesnt let him have this sort of stuff normally, so its a treat for him and he loves licorice.

Another idea is a gift voucher at a hardware store, if hes the handy type or maybe a movie voucher if he likes a good movie now and then. Thats also a treat for your Mum if they don't get out much. I couldnt do that option as my Dad just won a gold voucher that lasts a whole year, lucky duck! might have to borrow that sometime.......