The most basic weapon in Quake III is the gauntlet. It is an effective weapon at a very close range as it deals a lot of damage to the opponent if struck properly. If your strafing is good, then you can use a gauntlet against an opponent holding the rail gun. Avoid using it against rocket launchers, plasma guns or shotguns.

The default weapon is the machine gun. The damage it does is low but the accuracy rate is very high at both long and short range. Also the attack speed of the weapon is very fast. It is a good weapon to use to hunt down opponents running away at very low health.

Shotguns are very useful at short range. They cause damage depending on how accurate the shot is, up to enough damage to kill an opponent, in just two accurate hits. Though the damage is spread over an area around the target, it is best if you take your time to aim and get an as accurate hit as possible.

Plasma gun is most effective on medium range. It causes a lot of damage, has a high fire rate and is easy to use. Due to the high speed of the plasma and the fire rate it is best to aim directly at the target at closer ranges. At medium or longer range, fire a burst of plasma at a spread area, predicting the movements of the opponent.

Rocket launcher and rail guns are the two favorite weapons for all professional Quake III players due to their high amounts of damage. Rocket launchers have huge splash damage. At short range it is best to aim directly at the enemy. At medium or long range, predict the opponent's movements and try and aim at the ground below him or the any walls close to him.

No predictions are needed in railguns, it is all about accuracy. These are the hardest weapons to use but also the most damaging. It requires a lot of practice and control.

Every weapon has its own advantages and therefore to improve your game you must know how and when to use each weapon according to the situation. Gun switching is what separates a good player from a brilliant one.