Just Naruto's overuse of Rasengan.
His clothes (orange is not ninja!)
His strong sense of Justice (I have to save everyone!)
His Fighting style (charges at enemy with rasengan)
His obsession with Sasuke
His goal to become a hokage
All of the above
I already gave up on Naruto...let him die and get a new main character
His IQ for starters.
Other than that I would have to go with his fighting style.
I would really change the fact that no-one kills people. Every other Ninja village has the ability to kill people but Kohona. The only people who have killed are... Kakashi, Choji.
His fighting style is the most annoying thing... we know he'll become hokage eventually, so he should start acting like one!! He should get over his obsession with Sasuke too - people who've read ahead in the manga know what I'm talking about.