Ryuuken (doctorquicy) is human and not dead, but he is a Quincy and can sense spiritual presences and powers, etc. He can also see souls and stuff, too.

Sion (a_natural) is human, although he had a close brush with death which resulted in his white hair and red scar.

Luka (brandloyalty) is a Duras (demon) of a very high rank and has blood of the Demon King infused in his body. He's several hundred years old and still kicking.

Kanda (withoutregret) is a science experiment that was created to house the brain of a former exorcist. His Innocence (a holy substance that makes up his sword) is in his blood. Or something. IDK my bff D.Gray-man. He's died several times in canon.

Tatara (inlovingmemory) is super dead and knows it. He is imbued with the Red King's aura, which is something akin to fire, and has the power to manipulate it.

Nai (simplegifts) is a human/niji hybrid. He's got super hearing and some other stuff going on, but he's pretty normal and alive otherwise.