One that sends you back to a memory that you have stored in your brain that you pull out only for special occasions.
My mamaw used to sing this to me at night, during the day or just flat out tell me that she loves me a bushel and a peck. If you asked me to sing the rest of the song - I couldn't. But the words, "I love you a bushel and a peck, a bushel and a peck and a hug around the neck" are tattooed on my brain. I can feel the love as I type.
So, why don't you tell your Valentine, loved one, best friend or stranger, "I love you a bushel and a peck and a hug around the neck." I guarantee you'll get a smile back. And in the end, a genuine smile can be the best "change" the giver can receive.