The pick is a tools almost indispensable for the guitarist, (and sometimes, the bass player), so, here is what I use myself.
Jean-Charles Dugain is a guitarist but especially a big creator of picks !
His picks recognizes easily : they are in very singular materials : bone, polished stones, metal, precious stones… and even golden !
They are very stiff and almost indestructible !
But they are expensively and it's necessary to become used to their use.
Price for a pick in bone or stone : from $ 17,00 to $ 25,50.
I use them all the time with a preference for the bone.
The stone has a more suppressed sound and doesn't hang the ropes…
It's practical for the eased sounds and the accompaniments.
The bone hangs perfectly ropes and fingers and allows to have a powerful sound.
If you tested other materials, let know of what you think of it.