Average shoe size in the NBA is 15. This is what Lebron James wears (he is 6'8" tall).
Largest shoe size currently in the NBA is size 20.
Largest shoe size ever in the NBA was size 22 for Shaquille O'Neal (he is 7’1” tall). Compare this to Yao Ming, who was 4 inches taller yet wore shoes 4 sizes smaller (size 18).
Perhaps the most famous mismatch belongs to Michael Jordan. He wore size 13 on the right and 13.5 on the left.