These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Naruto: Clash of Ninja
Crowning Music of Awesome: Final Valley Version 2 from Revolution 2, found only when Naruto faces Sasuke in a one on one battle in the Final Valley stage. And yes, it returns in Revolution 3, when the two face off again. Considering by that point you're a fairly experienced player, this can make the battle a Crowning Moment Of Awesome as well if the match is between skilled players.
From the first game, Akumaru, who, being a dog, is so short that everyone's attacks go over his head.
Also exclusive to the first game, Crow. While he doesn't have many great combos, he doesn't flinch when attacked, so he can freely interrupt enemies' combos.
Sasuke with the Sharingan has a special which hits instantly and from across the map, with predictable results. He also has a regular combo which allows him to teleport behind his opponent and attack instantly, giving them no time to turn around and block.
Kabuto regenerates most of any damage he takes, effectively giving him far more health than anyone in the game. His combos aren't bad, either.
From Shippuden 3, Sasori's stinger attack lets him break his opponent's guard in one shot from across the screen, his regular combos are almost as powerful, and his special attack poisons the opponent on top of its substantial damage.