New Golf Balls. When it comes to golf balls, your new ones typically help you perform better on the course. If you're just practicing, you can use old balls or ones you don't necessarily care about.
Sun Screen/Bug Spray. One of the best reasons to play golf is to enjoy the sunshine. However, too much sun exposure can damage your skin and give you a painful sunburn. You'll also want to pack some bug spray to deter those pesky bugs from getting in your way.
USGA Rule Book. Having the USGA rule book handy in your bag is crucial if you want to take your golf game seriously. This way, you'll know important details like penalties and how far you can move your ball.