User blog comment:Godisme/Quiet Chamber, Noisy Heart/@comment-893506-20110913211105/@comment-4465398-20110921122006

"This would mark the first time that someone actually fought the shinigami in their true form in the canon. Any other time it was non." Uryu fought Renji at the end of season 1 as a Human, also the Arrancars that show up after the Rescue arc while he had lost his powers. Humans with "spiritual pressure" have been explained to be able to sense and see Souls and Hollows and such depending on how strong they are "spiritually aware".

(Late so please excuse my grammar/spelling/lack of other prime examples)