What in your opinion is the best paradox ever, and why?

That isn’t a paradox really, for the same reason that there can be no such thing as an irresistible force meeting an unmoveable object. A dog that can catch everything and a fox that can’t be caught can’t both exist at the same time, just like if there exists a force that can’t be resisted then necessarily that means there cannot exist an object that can’t be moved. So it’s not a paradox, it’s a false premise.