Naruto is know for it's large cast of lovable characters but as of episode 112 of the original series I can definitively say that Rock Lee is easily my favourite character in the series.
Everything from his positive demeanor, to his underdog background is so very beautifully shounen, he's so very cheesy with his background of fighting back against those who didn't believe in him, finding comfort in Might Guy and rising to become a splendid ninja. But what I think makes him special is just how genuinely sympathetic, yet still endearingly passionate in the face of absolute failure and misfortune he can be.
An example of what I've expressed comes from his legendary fight against Gaara in the preliminaries before the finals of the Chunin Exams. When he is defeated by Gaara we learn that he will never be able to return to being a shinobi due to the severity of his injuries, this causes Lee to question his future and everything up until this point becuase of his ethos being to never give up and that with hard work even he can become a splendid ninja but in spite of it all he keeps a positive outlook and whole heartedly believes he will one day recover with perseverance.
Eventually Naruto finds the legendary healer Sanin Tsunade who is famous for her healing capabilities, however she urges Lee to quit being a shinobi due to his only option being life threatening surgery, at this point, desperate for an answer he asks Might Guy what to do, in a highly emotional climax both Lee and Might Guy decide that in order to coninue his dream he must never give up as that is his nindo, his ninja way.
In the end he displays something so beautifully simple, that passion and perseverance will always pay off and that even in the worst of times we can continue to be better for ourselves and for those we love. Rock Lee is my favourite because he's corny and goofy and simple and so emblematic of what I love about shounen anime.