I know it seems pretty stupid, but I know at least one person who could have used a Ben&Jerry's pint lock, a combination lock that keeps your ice cream from being opened by others. One of my friends used to have a roommate who was so paranoid about someone eating her food, particularly her ice cream, that she'd lick everything, in plain view of everyone, before putting it away. Unsanitary, yes, but probably very very effective as well.

Ice cream hoggers who don't want to pre-lick their pints can pick up the lock for $5.50 at Ben&Jerry's.