"Game hard train hard"

fps_max

Frame rate limiter. This is what you want to mess with if you are going to have sucess increasing your fps. Goto console when you are in game and just mess with this, as it differs from computer to computer on what setting is best.
cl_allowdownload <0/1>

Client downloads customization files. Set to on by default, no reason not to have this so why not leave it like it is.
cl_allowupload <0/1>

Client uploads customization files. Well this is set to on by default but I am not sure if you want this unless you are trying to show off your new skin on a server that has this enabled. If not you can save some fps here by disabling this.
cl_autowepswitch <0/1>

Automatically switch to picked up weapons (if more powerful). Hey, I use this myself, why don't you. It really stinks when you are shooting someone with the pistol and you run over a gun and you have to reload it. You will get used to hitting 1 after you pickup the gun.
cl_c4dynamiclight <0/1>

Draw dynamic light when planted c4 flashes. Default set to off, so I think it should stay this way, at least valve thought about fps when they made the default for this.
cl_c4progressbar <0/1>

Draw progress bar when defusing the C4. Default set to on, you can save some more fps by disabling this as it is really not that usefull, whats the diffrence if you can see how much time is left anyway, not like you are gunna stop if you see something happen and you know you have a certain amount of time left anyway right?
cl_cmdrate

Max number of command packets sent to server per second. This is default set to 0 for unlimited. I wouldn't touch this unless you know what you are doing to reduce lag.

cl_updaterate

Number of packets per second of updates you are requesting from the server. The default is set to 20 for this and as with the cmdrate, I wouldn't touch this unless you knew what you were doing to try and reduce lag.
cl_crosshaircolor

Color of crosshair. 0=green, 1=red, 2=blue, 3=yellow, 4=skyblue. The default crosshair after installing CS:S is 0 for green. I like to leave this as default unless you like to have it another color as I have become used to this color.
cl_crosshairscale

Size of the crosshair. Lower value=Larger, Higher value=smaller. The default value for this is 768. Don't ask me how they randomly chose that number but if you want, you should set that down to around 400 to your liking so you can have an easier time getting those awsome headshots you have been wanting.
cl_crosshairusealpha <0/1>

Make crosshair translucent against similar colors. This is set to off as default. Not very helpfull in the lighted maps, in darker maps I could see how this might help.
cl_customsounds <0/1>

Enable customized player sound playback. This is default set to off as well.
cl_demoviewoverride <0/1>

Override view during demo playback. This is a great command to use if you are trying to make a video and are having some problems or need to override the demo. Awsome command.
cl_drawhud <0/1>

Enable the rendering of the hud. sv_cheats must be enabled to disable hud. On most servers sv_cheats are not enabled (when I say most I mean next to none) so I don't think this would be of much use unless you are messing around on your own server.
cl_showtextmsg <0/1>

Enable/disable text messages printing on the screen. This is set to on, and I really dont see why you would want to set this to off unless you are obsessed with those fps, this could help you in that department if you are willing to give up the server community.