Padlock the Ice Cream!
From our "wish I'd thought of that years ago" department: Doug Hertle was so worried about his roommates getting into his ice cream that he wrote to Ben & Jerry's to suggest that they sell their product in padlocked, stainless steel containers. They've now met him halfway: you can buy an ice cream bucket lock on their website.
(Doug also suggested making children's clothes out of Swiffer cloths. He says that since kids get into everything anyway, you might as well use them to clean the house...)