What did Hitchcock consider his best MacGuffin?

Hitchcock used the word MacGuffin to mean a pretext for a suspense plot, an object or secret, such as military plans, of vital importance to the characters but of no real importance to the filmmaker.

He thought his best MacGuffin was the set of vague “government secrets” in North by Northwest (1959), because this MacGuffin was “the most impertinent, the most nonexistent, and the most absurd.”