Paintball guns (also referred to as markers) are the very basis for the sport of paintball. They come in all shapes and sizes, but to play you only need something that propels paintballs in a somewhat straight line. Paintball guns can be bought new for less than $40 or rented for $10-$20 a day from many paintball shops.
Paintball masks exist for the simple reason of protecting your face. A flying paintball can leave a small bruise if it hits your body, but a direct shot in the eye can blind you. Make sure your mask is approved for paintball and then use it as if your eyesight depended on it.
Paintballs need to get into the chamber of your gun before you can shoot them and the best way to do this is with a hopper. A hopper is a small container that sits on your gun and feeds paintballs into your gun.
The propellant to fire a paintball comes from compressed gas - usually either compressed air or compressed carbon dioxide (CO2). Guns require one of two kinds of compressed air tanks: small 12 gram tanks that also are used in BB guns or larger tanks that screw onto the gun. A larger tank of CO2 or compressed air will be able to shoot hundreds of paintballs.
Along with paintball guns, paintballs are what make paintball possible. These spherical containers of paint are loaded into your gun and then shot by the expansion of compressed gas. Many different brands and colors exist, and more expensive usually means a better ball. For a beginner, though, they all perform about the same as long as they are not too old, so pick what looks good to you and use it. Be sure to bring enough to last as long as you want to play.
Suggested, but not required:
Clothing That Matches Environment
Wherever you are playing paintball, colors that match your surroundings will help you hide. Any clothes will work, but it's easier to play when you don't stick out like a cat in the dog pound.
Almost without fail, after playing a few games of paintball, people get thirsty. Come prepared with more water than you think you need and if you are prone to hunger or low blood sugar, bring something to munch on between games.
Screw Driver/Allen Wrenches
Most simple problems with paintball guns can be resolved with a Phillips head screwdriver and the proper sized Allen wrenches (hex keys). You may not always need them, but most days you will.
O-rings wear out and blow at the most inopportune times. They are used on tanks and inside your gun. Be prepared to replace them and get back in the game.