Got ugly fingerprints, dust or other detritus on your beautiful iDevice? Just get a small blob of Blu-tac (a.k.a. sticky tac/clay) and rub it on the screen. After a few rubs any marks will disappear. This is also good for giving the TouchID sensor a clean, and for getting rid of those ugly stripes that appear on an iPad screen from the creases of a Smart Cover.
For what it’s worth, this trick can be used to clean grime off virtually any surface. I just used it to clean years of accumulated human grease off the aluminum surround and the keys of my Apple Keyboard, for example.