While preparing to move, I found a bottle of Krud Kutter that I had bought over a year ago. I had not been impressed with it then but decided to test it again, and I immediately fell in love.
It felt magical as I cleaned smudges, drawings, finger prints, everything off of my walls, etc. It was like I had been given a wonderful gift.
A few people had recommended the magic eraser, which I absolutely love also - but this somehow worked even better.