Tommy Oliver

 Tommy was a powerful weapon of Rita Repulsa's army before breaking of her control and joining the Mighty Morphin' Power Rangers as the Green Ranger. He later breaks from Rita's control and fights against her with the rest of the Power Rangers. At one point Tommy loses his powers and grants control of the Dragon Dagger, Dragonzord and gold shield to the Red Ranger. He comes back as the White Ranger, shield and all. He later becomes the Red Ranger in another Power Ranger's series Power Rangers Zeo and Power Rangers Turbo and the Black Ranger in Power Rangers Dino Thunder
   
Fun Facts:
Longest Running Power Ranger to date.