The adult primary protagonists in Naruto typically have a high ninja rank or hold a reputation within and beyond their village. Hatake Kakashi is a Jounin class ninja and is known throughout the Naruto universe as the copy ninja; he has the ability to use any ninja technique or ninjutsu after only seeing it once.
As of the story arc in April 2011, Tsunade is the Hokage --- the Leaf Village's leader --- and is widely respected as the best medical ninja, one of the Leaf's three greatest ninjas and one of the best female ninjas.
Secondary protagonists play a minor role in the Naruto universe, either through a small constant supporting role or a limited appearance in a single story arc. Iruka Umino is a Chuunin class ninja and was Naruto's first teacher. He is regularly put in the story to give Naruto advice in dealing with life as an outcast. In the first Naruto Shippuden Arc, elder Chiyo was the representative from the Hidden Village in the Sand to support Naruto. She had a crucial role to save Gaara, the Sand's leader, with a resurrection jutsu in exchange for her own life.
Most of the main antagonists in Naruto are legendary ninjas who are feared across the land. They typically have a large bounty for their lives and are listed as the highest rank criminals in a ninja's hit book. Orochimaru, one of the Leaf's three greatest ninjas, betrayed the Leaf Village and came extremely close in destroying the village beyond repair. As of the story arc in April 2011, Uchiha Madara is the main antagonist of the series. As one of the oldest surviving ninjas, he plans on attaining the power to cast an illusion on all the people in the world --- effectively gaining control over the actions of each person.
There are several animal summons in the Naruto universe which have developed into fully-fledged characters. These animal partners exhibit human traits such as speech and the ability to use jutsus in combat. Gamabunta, Naruto's primary summon, is considered as the boss in the land of frogs. He has provided Naruto support in numerous battles and was crucial to saving the Leaf Village from Orochimaru's first attack. Pakkun is Kakashi's primary summon. As a ninja hound, he can track anyone miles away from the slightest hint of her scent.