The Microsoft Excel AutoSum button, shown as Σ on the toolbar intelligently guesses which cells you want to add up. It uses a very simple algorthm first scanning upward looking for cells with numbers and then if that fails looking to the left. It was first released around the same time as Clippy, but unlike Clippy obeyed rules of appropriate intelligence. When the sum algorithm gets the wrong selection it is no harder to change this to the one you want than if you had selected it yourself in the first place; that is it doesn't make things harder when it is wrong.
Also known as Microsoft Excel Sum button