Padme Amidala was supposed to have a theme, but apparently George nixed having a set-in-stone theme in Episode I so that he could have the solid love theme emerge in Episode II.
Boba Fett's theme is only heard in Episode V. It is a two-note bassoon motif and is heard quite frequently.
There are so many themes. Duel of the Fates, The Force/Obi-Wan's Theme, Anakin's Theme, Qui-Gon's Theme, Shmi's Theme, Emperor's Theme, Jar Jar's Theme, Darth Maul's Theme, Luke's/Star Wars Main Title Theme, Imperial Theme (E4), Rebel Fanfare, Princess Leia's Theme, Cloud City/Lando's Theme, Han Solo and the Princess Love Theme, Imperial March, Hyperspace Theme (Eternal Padawan's aforementioned three-note theme), Jabba's Theme, Droids' Theme, Yoda's Theme, Luke and Leia Family Theme, Ewok Theme, E4 Celebration Theme, Death Star Motif, Asteroid Chase Theme, and the Jawa theme.
I'm sure there's more, but that's all I can think of off the top of my head. That'll give you guys a bunch to choose from.
Mine is Luke and Leia Family Theme from Episode VI, followed closely by the Force/Obi-Wan's Theme.
NP: David Michael Frank's "The Mole"