The ProLapsGolf Club is a piece of golfing equipment and a melee weapon.
It has moderate power and long reach, allowing the player to attack several enemies providing they are close together. It can be swung whilst stationary, or running. The golf club is a very useful weapon to use on victims on the ground, as it is used very quickly once a person falls down.
In GTA Vice City, if the player attacks a person who is lying on the ground or dead, he swings the club as he would for a golf shot.
In GTA V although the club is not the fastest weapon in combat (as the knife hits faster) it seems to be the fastest weapon to hit while running, which means that if one person is going to attack another one while running using a knife and the other one is doing the same with a golf club, usually the one with the club will hit first (although that does not happen all the time, all depends on the player's reaction).