Best for drinking, or best for chucking at Fartage?
I'll be honest, I have never thrown a milkshake or, in fact, any fast food product, at anybody, so I can't really comment on the aerodynamic qualities.
McDonalds milkshakes tend to be highly viscous and are therefore probably very difficult to drink with the new paper straws, and so probably the only thing you can do is throw them at scummy arsehole people like Nigel Farage.
If I may connect this to a different thread, I think Nigel Farage constitutes an unpleasant subset all by himself.