Favorite character?
Mine would be the Mikami brothers.
Myself being fluent japanese, their accent sounds like they came from country area, mixed with a bit of Kansai dialect (or some hillbilly dialect from up north) and of course slang.
Miike gave them lots of funny one-liners and the things they mumble during the last fight was funny to me. Like it was just a game to them and having fun.
Their mannerism were also comical in a realistic way. I dont know if that makes any sense.