Things You Never Clean, But, Really, Really Should.   

Your cosmetics: Wipe down the rims of the bottles etc.
The Walls: Believe it or not your walls get dirty. You dust your furniture, so why not dust your walls. I use my Swiffer to do so.
The kitchen sponge: I personally don't use one. They harbor bacteria.
Your wooden cutting board: That board gets a lot of use. I wipe mine down with white distilled vinegar.
Bath tub toys: A breeding ground for bacteria. Wash with warm sudsy water. 
The bottom floor of your oven: That's a good one. I am doing this right now. Putting the items I store in the bottom in the dish washer as we speak.
Your mop: I don't use one. I get on my hands and knees and clean my bathroom floors with white distilled vinegar. I have tile porcelain floors.
Light switch plates: All those dirty finger prints can be wiped off with a clean rag.
Your umbrella: Prevent build up of mildew.
Your computer: Netfix will look 10x better.