Stock up on... cereal. I get good coupons and sales for different brands and flavors so it may look like I have cereal coming out of my ears but I am really just stocking up before that one goes off sale.
Run out of... if I dont stock pile muffins then I usually run out. My DDs only like the little choc choc chip muffins and only one store around here sells them. So when they get them in, I have to grab a bunch.