These are all females crossplaying as male characters, but... Natsumi Mitaka is the one who comes to mind for me. I totally thought she was such a hot guy as Yuki Kaito... until I saw her RomeCin!Miku cos lol. Aoi Takamura (well known for her Sakura Haruno) also crossplays (Shin Asuka, Prince of Tennis chars...). Arisa Mizuhara has also crossplayed (Cloud, Len, Hetalia).
Also, she's not Japanese, but Yuegene Fay (Thai) still confuses me. Akirago (Chinese) also made a pretty handsome boy, but I don't think she's very well known.
RIP CosRevo, Love Laugh, Sweety Pop, Cocosilver.