Who were the stand out free agents of the last 10 seasons?

 In professional sports, a free agent is a player who is eligible to sign freely with any club or franchise; i.e., not under contract to any specific team. The term is also used in reference to a player who is under contract at present but who is allowed to solicit offers from other teams. In some circumstances, the free agent's options are limited by league rules. 

Illustrated by Jasmina El Bouamraoui and Karabo Poppy Moletsane, CC0, via Wikimedia Commons