Little Expense, Big Savings: What's Your Favorite Frugal Buy?

We purchased this toothpaste squeezer doohickey for $0.99 cents about four months ago: 

Since then, we're buying way less toothpaste. It should save us quite a few bucks in the long-term, too, provided we don't lose it / the cat doesn't eat it / it doesn't get sucked into the sweltering pit of despair we call "outside right now."

Which leads us to this softball question for a fiery Friday:

Sweet readers, what's your favorite frugal buy?

Do tell! Pass it on!