Ron Weasley. I could wax poetic about this character for days. Why do I like him? I relate to him so well. He's a middle child. Yes, there's Percy, Fred, and George, but they find ways to deal with it. Ron doesn't. He has that classic middle child syndrome. His siblings have all etched out identities for themselves and Ron feels there isn't anything left for him. He's insecure. He's never sure if Hermione loves Harry more than she does him. He believes for the longest time that she would choose The Chosen One over him any day of the week. He sometimes feels his mother loves his sister and even more than him. His sister is the girl his parents always wanted. Sometimes he thinks Harry's the son his mother wishes she had. He doesn't feel he's worthy. It's not true, but try telling Ron that! He gets jealous easily. He's jealous of Viktor Krum taking Hermione to the Yule Ball. He's jealous of Harry for entering and becoming a Triwizard Champion. In the end, he always finds out he has nothing to be jealous about, but he has to learn his lesson first.
I also like Ron because he's funny. He's got some of the best lines in the books.
"When we come face-to-face with one down a dark alley, we're going to be having a shufti to see if it's solid, aren't we, we're not going to be asking, 'Excuse me, are you the imprint of a departed soul?"
"IF WE DIE FOR THEM, I'LL KILL YOU, HARRY!"
He's Harry and Hermione's connection to the wizarding world. They learn about it through him.
"Hearing voices no one else can hear isn't a good sign, even in the wizarding world."
Most importantly, he came back. Book 7, he left. But, he came back. He came back to Hermione. He came back to Harry. He came back to the Horcrux Hunt, to fighting Voldemort, to making sure the wizarding world would be a safer place to live.