I've been considering a guard goose for my chickens for many years. So loud though, not sure I want the extra racket and aggression.

Tangentially, if your guard geese aren't aggro enough, the Mute swan is an angry bird that is sometimes used to control geese. One even managed to drown a caretaker: https://abcnews.go.com/blogs/headlines/2012/04/killer-swan-b...