I"m going to force you guys to pick just one and why you chose that author/artist over the others. This can be an american artist, japanese, korean, tapastican, any other origin.... And let's assume you can communicate with each other, lol
It's hard for me too, but I'm going to have to go with Ishida Sui, hands down. His art and ideas are amazing and beautiful. His manga, Tokyo Ghoul and all its companions are all so in depth and well thought out. I really recommend reading them, and then watching the anime.
Sorry Slave In Utero, Tokeino Hari, ONE, 66 and about a hundred others... I love you guys but...