I have seen used cars with lots or registration stickers still stuck on their windshield. How on earth do we remove them? They may look cool to the present owner, but they certainly do not look cool to me.
Spray them with a glass cleaner and then try to scrape them off. Another thing that works well is vinegar. Mix hot water and vinegar together and spray it on the stickers. Something in the vinegar loosens up the glue and you can wipe them right off.
Using a small dab of olive oil or baby oil will work too. Don't use a lot though and be sure to clean the windows after getting the stickers off. Also, don't get it on your paint, the baby oil that is, because it will leave a mark.