Heiji Hattori

The only son of Heizo Hattori, Chief of Osaka Police Department. He has the same ability as Shinichi to make hypothesis, and also the West version of Shinichi (he is a famous high-school detective, too). He challenges Shinichi to solve a case, and (of course without any doubt) Shinichi wins.
Later realizes that Conan=Shinichi, when Conan use Heiji's body and voice to make the hypothesis (note the funny Kansai accent that Conan speaks). He suddenly wakes up, but just keep quiet to let Conan solves the case and get a proof that Conan=Shinichi. Note his mistake by calling Conan with "Shinichi", Ran always get suspicious but Heiji always can work out a way to trick Ran. A perfect detectives' duo with Conan.
PS: Another thing, his name means "second".