Magic Sponges are my favorite household tool. I always have a couple on hand and have used them for everything from removing melted fabric from my iron to cleaning crayon off of the walls.
I used to go through a few Mr. Clean Magic Erasers a month...at least. When we bought our house and moved in there was a lot of serious cleaning to be done. I used 4 magic erasers on the cabinets in the kitchen alone.