According to a NY State Court of Appeals ruling, you don't have to yell fore on the golf course.  A case before the court featured 2 former golfing partners, one hit the other prompting the suit.

Dr. Anoop Kapoor and Dr. Azad Anand were playing on a nine-hole Long Island course in October 2002 when Anand was hit in the head while looking for his ball on a fairway, blinding him in one eye. The seven judges on the state Court of Appeals, siding with lower courts, said Kapoor's failure to yell in advance of his errant shot from the rough did not amount to intentional or reckless conduct.

Testimony indicates Anand was about 20 yards away at a 50 degree angle when he was hit.  That's definitely shanking one!