Forget Etiquette to Play the 'Caddy Shack' Game
Caddy Shack gets its name from the movie Caddyshack (affiliate link), which included scenes of the caddies yelling during each others backswings and such to try to make each other mess up the shot. That's what the game Caddy Shack is about, too: make your opponent mess up the shot, so that you can post a lower score. Of course, your opponent will be doing the same stuff to you.
Stuff such as yelling during your backswing or just before impact. Walking through the line of your putt on the green. Standing in just the right spot to cast a shadow across your golf ball, and then doing jumping jacks to make the distraction even worse.
Anything goes. Anything that your group of golf buddies agrees on, anyway. If you play Caddy Shack, you almost certainly play it within your regular group of friends. You kinda have to be friends in order to forgive each other the otherwise friendship-threatening breaches of etiquette you'll be pulling on each other. Your group might allow anything, or it might prefer to put a least a few limits on potential actions (like, say, a rule that golfers cannot touch each other during the swing).
While etiquette is out the door within the group that is playing Caddy Shack, do remember that there might be other golfers on the course. Caddy Shack is a game best played on a course where the holes are not packed close together and on a day when the course is not busy. Distract each other in Caddy Shack, do not be a distraction to other golfers on the course. Also note that because you are trying to make your opponent(s) hit bad shots, playing Caddy Shack can lead to a longer round of golf.
There are some similar games that put limits on the types of actions one can take, or limit the number of times a specific distraction can be used. See Gotchas and Woof Handicap/Boo Handicap. The game called Noonan (in which golfers yell "Noonan!" to throw each other off) is another one that comes directly from the movie Caddyshack.
More golf games:
