There were a lot of characters in Summer Wars (even if most of them didn't do a whole lot), so here you can talk about your favorite ones.
For me there's the obvious answer of Kenji, he's just plain awesome, and barring his math skills, he reminds me a lot of myself. Beyond him though, I really liked Shota. He was an annoying guy, but in a charming way - though I wanted to smack him
Oh, and of course I loved the grandma. She was an awesome character with a lot of presence.