What is your favorite low-calorie snack?

I like popsicles because they are light in that they don't feel like I'm filling my stomach, which is an issue I have related to a chronic condition. They may not necessarily be low-calorie, but they take a while to consume, which may help if the point is to delay consumption enough to pass a craving. I usually grab normal ones, but they have sugar-free ones that may reduce the calorie count.