"Aside from the standard machine gun you're issued at the beginning of the game and the gauntlet that you carry with you at all times, there are a variety of other weapons scattered around the map. In order to completely own your opponents, you're going to need to grab these weapons and get proficient in their use! Here's a rundown of what's available and what their respective ammo boxes look like."Gauntlet :Utility: close combat only (narrow corridors and doorways, turning corners) or last-resort weapon (always available in normals mods), i use too for camper :p
Damage: direct damage, 50 hp in average (more with speed)
Other: you won a gauntlet medal and send a "humiliation" message (that destroy your enemies morale :p)
Have to add: avoid using it against rocket launchers, plasma guns or shotguns

and straf help lot!
More infos: splash damage : none
*, radius damage : none, reload time : 400 msecs, switch time : 450 msecs, holdable ammunition : endlessly, none ammunition.
Machine Gun :Utility: long range : maybe the best way to kill a player who running away and are to far for your lightning gun
(if you don't have railgun), it deals aim knockback.
Damage: 7 hp per bullet
(in team deathmatch only 5hp) with a rate of ten shots per second BUT has small degree of spread
(approx. 2 degrees) so you will probabely have some lost shots :p
More infos: reload time : 100 msecs, switch time : 450 msecs, splash damage : N/A
*, splash radius : N/A, holdable ammunition : 200, ammuntion pack contain : 50.
Shotgun :Utility: close range combat
(because its large spray diminishes damage with distance) [very useful is space maps like ctf4ish]
Damage: shoots 11 pellets that deal 10 damage each (so a concentrated spread can kill an unarmoured player (110 hp)

)
Other: don't forgot you have one second delay between shots with this weapon!
More info: splash damage : N/A
*, splash radius : N/A, reload time : 1000 msecs, switch time : 450 msecs, holdable ammunition : 200, ammunition pack contain : 10.
Grenade Launcher :Utility: useful when somebody is hide and you know his position

, use to barricade entrances and force enemy to take another route
(spam corridors where you think the enemy will be, spawn points and the entrances to rooms, or exits of teleporters, for protecting the flag).Damage: detonate on contact with another player or 2.5 seconds after being launched, direct damage : 100 hp
Other Fires at a rate of 0.8 seconds
More infos: splash damage : 1 to 99
*, splash radius : 150, reload time : 800 msecs, switch time : 450 msecs, holdable ammunition : 200, ammunition pack contain : 5.
Rocket Launcher :Utility: medium to long range weapon (for close combat splash damage will hit you too)
Damage: direct hit deals 100 damage
Other: rocket jumping (good way to get out of the enemies base

), speed of one rocket: 900-1000ups
Have to add: 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.
More infos: splash damage : 1 to 99
*, splash radius : 120 (you see that by shooting the ground before foot's ennemies do more damages :p), reload time : 800 msecs, switch time : 450 msecs, holdable ammunition : 200, ammunition pack contain : 5
Lightning gun :Smite your enemies with the hand of Zeus !
Utility: (...) knock back effect on your opponent, so you can hold your opponent in lava, slow down ennemy etc.
Damage: can kill a healthy opponent in less than two seconds because it shoots at 0.05 seconds per pulse, the only requirement is that you need a steady hand to concentrate the ray upon your opponent
Other: if other shoot you with LG : be either far away (try to escape it with for example rocket jump and then use like mg from distance), or really close, approach left and right at a diagonals and zig zag !
About cg_truelightning <0.0 - 1.0> (default = 0.0) A value of 0.0 is just like the baseq3 version "feel" of the lg. A value of 1.0 imposes no lag at all (shaft is always rendered on the crosshairs). A value of 0.5 is a good mix of the two to reduce the wet-noodle effect, while still maintaining consistency of where the server actually sees the shaft.More infos: switch time : 450 msecs, splash damage : N/A
*, splash radius : N/A, holdable ammunition : 200, ammunition pack contain : 60.
Rail gun :Utility: long range combat or sniping
(weapon of choice for those with careful aim and/or a good connection)Damage: inflicts 100 direct damage but has a low fire rate (default 1.5 seconds)
Other: you can make your team faster with shooting them (useful for catch flags) and if somebody jump in your head and jump by shooting him you can make him jump hight wall :zwinkern: ; two consecutive shoot give 'impressive medal'
Other: if other shoot you with RG : either switch to MG/PG, or get close. Strafe left and right to make it harder to hit you!
More infos: splash damage : N/A
*, radius damage : N/A, reload time : 1500 msecs, switch time : 450 msecs, holdable ammunition : 200, ammunition pack contain : 10.
Tips: most of time it's easily when you have shoot first rail and the player is still alive (because of armor,...) to change weapon and use machine gun or lightning gun (for example) it take 450 msecs in place of waiting reload (1500 msecs) and not be sure to succeed with second rail :p
Plasma gun :Utility: close to medium range combat, in places where your opponent has limited horizontal movement ability or distracting/confuse opponents with bright and huge plasma balls
(block the enemys view) or really good too when enemy doesn't see you

.
Damage: direct damage : 20 hp per orb and 10 shoots per second
Other: plasma climbing :zwinkern:, speed of one plasma orb 2000 ups, only takes one bolt to get through the window in oa_bases3
Have to add: at medium or longer range (doesn't lose its power in long range :zwinkern:), fire a burst of plasma at a spread area, predicting the movements of the opponent!
More infos: splash damage : 1 to 15
*, splash radius : 15, reload time : 100 msecs, switch time : 450 msecs, holdable ammunition : 200, ammunition pack contain : 30.
BFG : (overpowered?)Utility: All ! ! !
Damage: 5 shots per second, which inflict damage and splash damage 100 hp per cell
Other: can also be use to make higher jump :zwinkern:
More info: splash damage : 1 to 99
*, splash radius 120, reload time: 200 msecs, switch time: 450 msecs, holdable ammunition : 200, ammunition pack contain : 15.
* Splash damage is damage taken by people near the point of impact
You normally start with gaunlet (endlessly ammunition) and machine gun (100 munitions).
- Taking shotgun weapon give you too 10 munitions.
- Taking grenade launcher weapon give you too 10 munitions.
- Taking rocket launcher give you too 10 munitions.
- Taking lightning gun give you too 100 munitions.
- Taking rail gun give you too 10 munitions.
- Taking plasma gun give you too 50 munitions.
- Taking BFG give you too 20 munitions.
If you never have had a weapon take munitions do nothing...
Now you know all you must for switching weapons, never have low weapons, wat cost rocket jumps etc (look the splash damage),...
The rest is question of training, config, reflex,... and luck

Hope that can help you

Happy frags !
"Don't just jump into battle, make sure you are fully equiped. Get a few good weapons, some health and armour.""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."(correction of errors? ; something to add? ...all other infos are welcome

)