One user, two passwords?

[MLA]

    I'm toying with a couple of ideas for security, and was wondering if it's 
possible to assign a user two passwords, each with different levels of 
permissions. For example, password A is for normal login, maybe some 
administrative tasks, while password B is the key to the kingdom, rm -rf / 
kind of power. I've been looking through the documentation on sudo, but 
haven't found anything relevant yet. I suppose the first question I should 
ask is if it's even possible to have two passwords?
    :Peter