From the question How does auto-pickup work?, we know that ammo is shared between players in co-op. How does this sharing work? Does each player get the full amount of ammo, or is it divided between them? Does it make a difference if one player already has full ammo of the type being picked up?
I'm also interested in the sharing of money and Eridium, but I believe those are covered in How does experience work in co-op?