Rubber spatula
Sure, you clean it every time you use it, but you should consider adding an important step: pulling the spatula head off the handle before you wash. Forgetting to do so is one of the reasons the NSF declared the rubber spatula the number-two dirtiest kitchen item. It was found to contain E. coli, yeast, and mold—not things you want to mix into your batter.
Stay safe: If your spatula is detachable, wash both pieces separately. If it's a one-piece, you still need to take precautions because yeast can hide and grow in the joint. Make sure to give extra TLC to that section when washing.