I am inclined to nominate the Arisaka bolt safety. It's very difficult to engage/disengage without a scope, and nearly impossible to manipulate with a scope eyepiece mounted over it. Consequently, the shooter is pretty much required to hunt with an empty chamber.
Then, the original Mauser safety mounted on the bolt does block the firing pin in two positions, so it is equally safe with the bolt locked and unlocked to permit loading/unloading withe safety engaged.
