The blender
You know to wash your blender every time you make one of your yummy spinach smoothies, but you're probably skipping one of the most important parts: the blender gasket (the rubber ring that helps hold the blade in place). In a 2013 report by NSF International, an independent organization that tests the health and safety of consumer products, the blender gasket was found to be the third germiest item in the kitchen, harboring Salmonella, E. coli, yeast, and mold. When researchers asked people what they thought were the top sources of grime in their kitchen, the blender didn't even make their list.
Stay safe: After sucking down the smoothie, the NSF recommends disassembling the blender and pulling the blade and gasket out for a thorough washing. Yes, every time.