"You will die" vs "You shall die?"

The will/shall distinction is both vague and controversial but the general consensus is that shall indicates intent, obligation, or duty, while will refers to simple futurity.

To anyone who subscribes to this dichotomy, the sentence "You will die" is an unarguable observation about human mortality, but "You shall die" is nothing less than a threat.

Edit I have heard people prescribe shall for first person and will for second and third, but I have never, ever heard anyone following that recommendation. Ditto with using "will" to mean intent for first person.

In the song "We Shall Overcome", the singers are announcing their resolve, not smugly predicting victory. My favorite line in The Devil Wore Prada, a movie full of witty lines, comes from this exchange.

Andy: Wish me luck!

Emily: No. Shan't.

I am going to use that line at some point. "Have a good day!" "No. Shan't."