A cocktail made with half draft beer and half gin-and-tonic (with ice). Also the name for what happens to you after consuming a few knife helmets.
Ralph: "Man, I went to the Snug last night and ordered way too many knife helmets."
Chris: "How you feeling?"
Ralph: "Like I wore a knife helmet."
A drink that is a mix of beer (draft) and a gin and tonic, served over ice.
Imbiber: Two Knife Helmets please
Bartender: Any preference for beer or gin?
Imbiber: One with PBR and Bombay Sapphire, the other with High Life and Hendricks