idiom. At the drop of a hat.
Real citation: “Free societies are hopeful societies. And free societies will be allies against these hateful few who have no conscience, who kill at the whim of a hat.”
(George W. Bush, “Bushism of the Day,” Slate, Sept. 17, 2004, http://slate.msn.com/id/2106877/)
Made-up citation: "Fellow evil-doers, be ready to smite the money-humping freedom monkeys. Be ready at the whim of a hat!"