Each film features a scene of severance, both physical and thematically. Someone loses a limb in each film and in most of them there is a separation of sorts, a severance from one's life or loved ones. Luke 'severs' his ties with Tatooine, Han is 'severed/separated' from his friends, Luke & Leia are separated from their friends in 'Jedi' and so on.
Physically the choices are obvious - Walrus Man's arm, Luke's hand, Vader's hand, Darth Maul's torso, Jango's head, Anakin's arms and legs. The list goes on and on.
I think that the severances in the Star Wars Universe are really thematically interesting and symbolic of many, many things taking place in the context of the films.