Ai Haibara is my definite favourite (:
Other favourite main characters Conan/Shinichi, Ayumi, Kaito Kid, Yukiko and Agasa.
Out of the government force & other famous detectives my favourite is Wataru Takagi.
Other favourites Chiba, Yumi, Sato and Jodie.
Lastly my favourite out of the B.O would be Vermouth.
I also like Akemi as well.