I have a huge bar or Dairy Milk hidden behind the flour and sugar in my 'baking cupboard'. DH or the kids will NEVER find it there. I enjoy having a single square very occasionally with a cup of coffee . If DH got wind of it, it would be gone in less than an hour..... 
Oh, and my 'hidden' £1 coins in the secret drawer under the seat in the car - for emergency parking/ supermarket trolleys etc.
What's yours?