Usually attacking midfield, the "number 10" is usually the most dynamic player on his respective team
Midfield
Richie McCaw plays 0penside flanker wearing the number 7 jersey
On his first goal scored for Barca he was wearing the number 30 jersey. He also appears in photos wearing the number 19 jersey before taking the number 10 jersey in 2008 upon the departure of Ronaldinho.
Sachin Tendulkar
no body
No player is currently wearing # 52 on Detroit.
He is currently wearing jersey number 88 with the Dallas Cowboys.
Antonio Cassano is wearing No.10 right now.
Fernando Torres.
Tim Howard, the former professional soccer goalkeeper, is best known for wearing the number 1 jersey during his career, particularly while playing for the U.S. Men's National Team and clubs like Manchester United and Everton.
His official number is 23 but when his jersey got stolen he wore a number 12 jersey
Depends on local tradition. Most places I have seen (Philadephia PA) 13 is worn by the outside center. It could however be one of the back wings.