A goofmeister is one who engages in the goofiest of acts--a master of goofery.
That guy is such a goofmeister that he ran through the supermarket with nothing on but a red cape.
A goofmeister is a person who presents a specific type of goofy behaviour in serious situations. It is easily noticed by individuals surrounding the goofmeister, which will either cause them to ignore his immature acts or admire him for his goofery.
Taylor is the goofmeister of the team, he always does stupid shit when we're supposed to take it seriously !