I nominate the Handsome Blue Beast of Konoha, Guy-sensei. We all know that he doesn't have those flashy ninjutsus and whatnot, but he have the Passion of Youth which makes him a gteat candidate for the job. Just him hearing the job description will burn his passion up. Guy-sensei is the most sencere ninja, not just in Konoha but throughout the shinobi world. He may seem silly and dumb, but never underestimate him, he can do things better than anyone else in the village. He will be tired, yes since he's also a human being despite being a ninja, but whe he's reminded of the teason why he's doing this job, he'll overcome his limit and push himself to finish his job thoroughly.

Sorry, there are some typos.