/!\ Warning /!\

1: Make a backup of your configs: qzconfig.cfg & repconfig.cfg !
If you don't do that and your config are broken, you can only blame yourself.

2: These commands don't change in any way your resolution.
They were tested on 3 different pcs.

3: This is just a guideline, not the sacre bible.
If i made some mistake or you have some suggestions / useful tricks, please let me know.

set cg_allowTaunt "1"
// If you want or not listen taunts

set cg_announcerTiesVO "1"
set cg_announcerRewardsVO "1"
set cg_announcerLeadsVO "1"
set cg_announcerLastStandingVO "1"
set cg_announcer "3"
// Various settings of announcer

set cg_blood "0"
// Not sure. Blood on screen i think

set cg_bob "0"
// removes bobbing while moving (bobbing = the slightly moving up/down from your screen as you walk)

set cg_brasstime "0"
// Amount of time expelled shells remain on screen.

set cg_buzzerSound "0"
// When set to 1, an loud buzzer sound will play when the match ends

set cg_drawCheckpointRemaining "0"
// Only in race

set cg_drawProfileImages "0"
// Don't show peoples steam avatars in game

set cg_drawcrosshairnames "0"
// Deprecated

set cg_drawgun "0"
// “0” will hide your weapon – “1” will show your weapon, but swaying as you walk – “2” will show your weapon and it will not sway as you walk – “3” will show a translucent weapon model.
// I like 3 but 0 is better for performance

set cg_drawRewards "0"
// Show reward icons and sound

set cg_enemyCrosshairNames "0"
// Draw the name of players above the crosshair when targetting them

set cg_forceEnemyModel “keel”
// Force all enemy models to be the same model.
// I suggest keel, because he's noisy but you can use “tankjr” if you want a more visible model

set cg_forceEnemySkin "bright"
// Opponent is brighter !

set cg_gibs "0"
// Controls the number of sparks when gibbing a dead body.

set lightningImpact "0"
// Enables lightning impact affect on surfaces by lightning gun

set cg_lightningStyle "5"
// 1 = Default Q3/QL, 2 = QuakeWorld inspired, 3 = Team Arena shaft, 4 = Thin shaft & 5 = Wide beam (Q3 style)

set cg_lowAmmoWarningSound "0"
// 0 = Disabled, 1 = Low Ammo Clip Reload Sound played for Low Ammo, No Ammo Click Sound played for No Ammo, 2 = No Ammo Click Sound played for both Low and No Ammo.
// Personally i use 1

set cg_lowAmmoWeaponBarWarning "0"
// Controls the weapon bar ammo warning display. (I prefer 2)
// 1=Draw weapon bar ammo value in red when empty, 2=Draw weapon bar ammo value in yellow when low and red when empty

set cg_impactSparks "0"
// Causes the enemy to spark when they are hit by any non-explosive weapons

set cg_marks "0"
// Render bullet marks on walls

set cg_muzzleFlash "0"
// Shows a muzzle flash when firing a weapon.

set cg_noplayeranims "0"
// I suggest to keep this on. Disables player model animations, showing only the 1st frame in the models animation sequence. 0=off, 1=on

set cg_playerNames "0"
// Draw targeted player names while in spectator mode, both in freecam and first-person mode

set cg_plasmaStyle "1"
// 1 = No Trail, 2 = Particle Trail

set cg_playvoicechats "0"
// Enables voice chats

set cg_railStyle "1"
// Railgun trail effect: 1 = Rail core rail trail, 2 = Spiral rail trail

set cg_railTrailTime "400"
// The time (in milliseconds) that rail trails are displayed for. 400 default.
// 0 min, 2000 max

set cg_rocketStyle "1"
// Rocket trail effect: 1 = No Plume, 2 = Fire Plume

set cg_scorePlums "0"
// Show floating score plums

set cg_screendamage "0"
set cg_screenDamageAlpha "0"
set cg_screenDamageAlpha_Team "0"
// Turn off completely the screen blinking red when you taking damage

set cg_shadows "0"
// Players shadow

set cg_simpleitems "1"
// Replaces pickup 3D models with iconic 2D images.

set cg_simpleitemsbob "0"
// Static items

set cg_smokeRadius_RL "4"
set cg_smokeRadius_NG "1"
set cg_smokeRadius_haste "8"
set cg_smokeRadius_GL "8"
set cg_smokeRadius_flight "8"
set cg_smokeRadius_dust "24"
set cg_smokeRadius_SG "0"
// Smoke of weapons / dust / Power Up

set cg_specNames "0"
// Looks like the same thing of cg_playernames

set cg_teammateNames "1"
// Teammate names...

set cg_useItemMessage "0"
// Enables drawing of the "No Item to Use" message when lacking a holdable item but attempting to use it

set cg_useItemWarning "0"
// Enables playing of the "No Item to Use" sound when any player is lacking a holdable item but is attempting to use it.
// I suggest to use 1

set cg_waterWarp "0"
// Water distortion off

set com_blood "0"
// Blood off

set com_hunkmegs "256"
// More ram. "512" work for me

set com_introplayed "0"
// Disables the playing of intro movie when loading game.

set com_idleSleep "0"
// Use sleep frames to reduce CPU usage.

set com_maxfps "60"
// Depends on your pc

set con_scale "1"
// No impact on fps. Change to 1 just if you wanna read more clearly

set con_speed "1"
// Slow console drop. Pc can take it easy

set r_allowExtensions "1"
// Use OpenGL extensions and r_ext cvars... keep it on !

set r_displayRefresh "60"
// Depends on your monitor

set r_colorbits "16"
// 16 bit colors

set r_depthbits "16"
// 16 bit color depth

set r_detailtextures "0"
// Any code labeled as detail in a texture is not used

set r_dlightBacks "0"
// Lighting values constant for dark and light areas

set r_drawSun "0"
// Controls the way in which lighting of models and objects is handled by simulating effects of sunlight

set r_drawSkyFloor "0"
// Enables a visual fix of the glitchy scrolling sky floors, removing the 'hall of mirrors' effect

set r_dynamiclight "0"
// Enables dynamic light from rockets, Quad, Flag, etc.
// Fixed dynamiclights: 1, use original broken code: 2, debug: 3

set r_fullbright "1"
// Renders all textures on the map at same brightness
// I suggest to turn off: r_mapOverBrightBits "0" & r_overBrightBits "0" and use that

set r_ext_compiled_vertex_array "0"
// Enables hardware compiled vertex array rendering

set r_ext_compressed_textures "1"
// Enables the external texture compression

set r_ext_gamma_control "1"
// "0" stops the gamma been set externally to quake

set r_ext_multitexture "0"
// No multitexturing

set r_ext_texture_env_add "0"
// Enables additive blending when using multi-texturing

set r_facePlaneCull "1"
// Enable culling of brush faces not in view (0 will slow FPS)

set r_fastsky "1"
// No sky's textures, just all black

set r_finish "0"
// Try setting this to 1 if you have laggy inputs.
// Enable extra completion code necesssary for some video cards, may decrease FPS

set r_flares "0"
// Enables projectile flare and lightning effects

set r_ignoreFastPath "0"
// Enables ignoring of Tess fast paths

set r_ignoreGLErros "1"
// Enables ignoring of OpenGL errors in an attempt to continue rendering

set r_ignorehwgamma "1"
// Enables ignoring of hardware gamma settings

set r_inGameVideo "0"
// Enables in-game videos.

set r_intensity "1"
// Intensifies the level of brightness added to textures and model skins

set r_lodCurveError "250"
// This setting determines how close you have to be towards a polygon before it "clips".
// Think of it as similar to Mip - Mapping.

set r_mapoverbrightbits "0"
// This is a setting which controls how bright the scenary, textures and objects are.

set r_overBrightBits "0"
// Ambient lighting applied to in-game entities or objects

set r_primitives "2"
// Sets rendering method.
// Valid settings: -1=skips drawing / 0=uses glDrawelements if compiled vertex arrays are present or strips of glArrayElement if not / 1=forces strips / 2=forces drawElements

set r_roundImagesDown "10"
// Set rounding down factor (larger = faster, lower quality)

set r_simpleMipMaps "1"
// Enables simple MIP mapping

// set r_subdivisions "80" <- Not writable
// Basically sets the "smoothness" of curves. 4 high, 80 low

set r_stencilbits "0"
// Disable stencil buffer

set r_swapinterval "0"
// Vertical synchronization, has mouse lag don't use for playing

set r_lightmap "0"
// Enables the light data lighting model

set r_vertexLight "0"
// Toggles vertex lighting.
// Enabling would mean disabling lightmapping: 0=disables, 1=enables

set r_lodbias "2"
// Sets Level-Of-Detail bias.
// An example would be the complexity of weapon rendering. -2=highest details, 2=low details

set r_textureBits "16"
// 16 bit textures

set r_textureMode "GL_NEAREST"
// Sets texture filtering mode.
// Possible extensions used: GL_NEAREST (nearest interpolation filtering), GL_NEAREST_MIPMAP (nearest interpolation filtering with mipmapping), GL_LINEAR (linear interpolation filtering), GL_LINEAR_MIPMAP_NEAREST (linear interpolation filtering with nearest (bilinear) mipmapping), GL_LINEAR_MIPMAP_LINEAR (linear interpolation filtering with linear (trilinear) mipmapping)

set r_enablePostProcess "0"
// Enables post processing, which offers extra graphical features and quality

set r_enableColorCorrect "0"
// Enables color correction when r_enablePostProcess 1

set r_enableBloom "0"
// Enables light bloom effects when r_enablePostProcess 1

set s_ambient "0"
// Environment sounds off

If you wanna do some research:

http://www.terta.de/lwt/docs/q3commands.html
http://quake3tweaks.tripod.com/commands.html
http://lizard.artun.ee/~korc/txt/Q3Tweak_3.html
http://www.esreality.com/post/2728622/quake-video-settings-feedback-pls/
http://www.planetquake3.net/tweak/fps_commands.html
http://www.esreality.com/index.php?a=post&id=756439
http://www.gamesurge.com/pc/hardware/tweaks/q3atweak.shtml
http://www.urbanterror.info/forums/topic/27800-old-computer-and-very-low-fps/