you would probably have to have two different binds that have two different configs like
bind k "exec viewon"
bind l "exec viewoff"
really the only way that i know of

Wow thanks for the fast reply!
I thought of that possibility, however it would be better if there is a way to do this with one key :/

bind j view
alias viewon "exec viewmodall; alias view viewoff"
alias viewoff "exec viewmodmelee; alias view viewon"
viewoff

I think you can do like exec viewmodelon toggle; viewmodel off"
Or something like that, I'm gonna let guys that knows this explain it a little better/telling you that it is impossible

EDIT: The post above me is what I meant

You can simply do this:

bindtoggle <key> r_drawviewmodel;

Every time you hit that key, you turn viewmodels on/off, depending on it's previous state (1 -> 0 or 0 -> 1)

I have now Idea how, but it works! Thanks!
Here are the scripts I ended up using, in case somebody wants to know :)
-----------------------------------------------------------------------------
Paste this into you autoexec.cfg :
unbind "KEY"
bind "KEY" view
alias viewon "exec viewmodall; alias view viewoff"
alias viewoff "exec viewmodmelee; alias view viewon"
viewoff
-----------------------------------------------------------------------------
create a new .cfg file named viewmodall.cfg and paste this:
r_drawviewmodel 1
alias wep1 "slot1; wep1com; alias mouseup wep-3; alias mousedown wep2; alias quickswap wep-3; alias lastwep wep1; keybind1"
alias wep2 "slot2; wep2com; alias mouseup wep-1; alias mousedown wep3; alias quickswap wep-1; alias lastwep wep2; keybind2"
alias wep3 "slot3; wep3com; alias mouseup wep-2; alias mousedown wep1; alias quickswap wep-2; alias lastwep wep3; keybind3"
alias wep-1 "slot1; wep1com; alias mouseup wep-3; alias mousedown wep2; alias quickswap wep2; alias lastwep wep-1; keybind-1"
alias wep-2 "slot2; wep2com; alias mouseup wep-1; alias mousedown wep3; alias quickswap wep3; alias lastwep wep-2; keybind-2"
alias wep-3 "slot3; wep3com; alias mouseup wep-2; alias mousedown wep1; alias quickswap wep1; alias lastwep wep-3; keybind-3"
alias keybind1 "alias key1 wep1; alias key2 mousedown; alias key3 mouseup"
alias keybind2 "alias key1 mouseup; alias key2 wep2; alias key3 mousedown"
alias keybind3 "alias key1 mousedown; alias key2 mouseup; alias key3 wep3"
alias keybind-1 "alias key1 wep-1; alias key2 mousedown; alias key3 mouseup"
alias keybind-2 "alias key1 mouseup; alias key2 wep-2; alias key3 mousedown"
alias keybind-3 "alias key1 mousedown; alias key2 mouseup; alias key3 wep-3"
alias mouseup "wep-3"
alias mousedown "wep2"
alias quickswap "lastwep"
alias lastwep "wep2"
alias key1 "wep1"
alias key2 "mousedown"
alias key3 "mouseup"
alias key4 "slot4; extrakey"
alias key5 "slot5; extrakey"
alias extrakey "alias mouseup wep-3; alias mousedown wep1; alias quickswap lastwep; alias lastwep wep3"
alias wep1com "r_drawviewmodel 1"
alias wep2com "r_drawviewmodel 1"
alias wep3com "r_drawviewmodel 1"
//BACKUP
bind MWHEELUP mouseup
bind MWHEELDOWN mousedown
bind Q quickswap
bind 1 key1
bind 2 key2
bind 3 key3
bind 4 key4
bind 5 key5
---------------------------------------------------------------------------------
create a new .cfg file named viewmodmelee.cfg and paste the stuff from above again,
but change:

alias wep1com "r_drawviewmodel 1"
alias wep2com "r_drawviewmodel 1"
alias wep3com "r_drawviewmodel 1"

to

alias wep1com "r_drawviewmodel 0"
alias wep2com "r_drawviewmodel 0"
alias wep3com "r_drawviewmodel 1"

and you are done :)
--------------------------------------------------------------------------------
There is only one small problem: If you press the key to toggle the viewmodel stuff, the last used weapon or quickswitch will be changed to you secondary!
However, that should be easy to fix, since it is a problem with the stuff in the viewmodmelee.cfg and in the viewmodall.cfg. Could someone please help me fixing this?

man there gotta be an easier way

bind f oneno

alias onevm "bind MWHEELUP onevmbind; bind f oneno; r_drawviewmodel 1"
alias oneno "bind MWHEELUP onenobind; bind f onevm; r_drawviewmodel 0"
alias twovm"bind e twovmbind; bind f twono; r_drawviewmodel 1"
alias twono "bind e twonobind; bind f twovm; r_drawviewmodel 0"
alias threevm "bind MWHEELDOWN threevmbind; bind f threeno; r_drawviewmodel 1"
alias threeno "bind MWHEELDOWN threenobind; bind f threevm; r_drawviewmodel 0"
alias onevmbind "slot1; r_drawviewmodel 1; bind f oneno"
alias onenobind "slot1; r_drawviewmodel 0; bind f onevm"
alias twovmbind "slot2; r_drawviewmodel 1; bind f twono"
alias twonobind "slot2; r_drawviewmodel 0; bind f twovm"
alias threevmbind "slot3; r_drawviewmodel 1; bind f threeno"
alias threenobind "slot3; r_drawviewmodel 0; bind f threevm"
bind MWHEELUP onevmbind
bind MWHEELDOWN threevmbind
bind e twovmbind

Is what I have. Then in every class, I can re-alias the binds so I have changing crosshairs, etc, and have a default viewmodel setup on every class (shotgun off for soldier, all on for spy). F simply toggles the given weapon's viewmodel. So if I have my rocket out, I toggle, and then the rocket will remain viewmodel off until I change class/restart the game.

Is that what you were after?

Also, because there isn't any exec, i think it avoids lag (i never used many execs, so not sure whether they lag).

I used command, however I wanted an automatic version :)

OK here is a working version (lines beginning with # are instructions):
---------------------------------------------------------------------------------
#Copy&Paste this into you autoexec.cfg (change KEY to the Key you want):
unbind "KEY"
bind "KEY" view
alias viewoff "exec viewmodmelee; alias view viewon"
alias viewon "exec viewmodall; alias view viewoff"
viewon
---------------------------------------------------------------------------------
#now create a config called "viewmodmelee.cfg" and Copy&Paste this:
r_drawviewmodel 0
alias crossmodel1 "r_drawviewmodel 0"
alias crossmodel2 "r_drawviewmodel 0"
alias crossmodel3 "r_drawviewmodel 1"
alias qcom1 "slot1; crossmodel1; q1from2; 2from1; 3from1"
alias qcom2 "slot1; crossmodel1; q1from3; 2from1; 3from1"
alias qcom3 "slot2; crossmodel2; q2from1; 1from2; 3from2"
alias qcom4 "slot2; crossmodel2; q2from3; 1from2; 3from2"
alias qcom5 "slot3; crossmodel3; q3from1; 1from3; 2from3"
alias qcom6 "slot3; crossmodel3; q3from2; 1from3; 2from3"
alias q2from1 "bind q qcom1"
alias q3from1 "bind q qcom2"
alias q1from2 "bind q qcom3"
alias q3from2 "bind q qcom4"
alias q1from3 "bind q qcom5"
alias q2from3 "bind q qcom6"
alias com1 "slot2; 1from2; 3from2; q2from1; crossmodel2"
alias com2 "slot3; 1from3; 2from3; q3from1; crossmodel3"
alias com3 "slot1; 2from1; 3from1; q1from2; crossmodel1"
alias com4 "slot3; 1from3; 2from3; q3from2; crossmodel3"
alias com5 "slot1; 2from1; 3from1; q1from3; crossmodel1"
alias com6 "slot2; 1from2; 3from2; q2from3; crossmodel2"
alias 2from1 "bind 2 com1"
alias 3from1 "bind 3 com2"
alias 1from2 "bind 1 com3"
alias 3from2 "bind 3 com4"
alias 1from3 "bind 1 com5"
alias 2from3 "bind 2 com6"
bind 1 "slot1; r_drawviewmodel 0; 2from1; 3from1; crossmodel1"
bind 2 "slot2; r_drawviewmodel 0; 1from2; 3from2; crossmodel2"
bind 3 "slot3; r_drawviewmodel 0; 1from3; 2from3; crossmodel3"
----------------------------------------------------------------------------------
#create a second config called "viewmodall.cfg" and Copy&Paste the same thing exept #change this:
r_drawviewmodel 0
alias crossmodel1 "r_drawviewmodel 0"
alias crossmodel2 "r_drawviewmodel 0"
alias crossmodel3 "r_drawviewmodel 1"
#to this:
r_drawviewmodel 1
alias crossmodel1 "r_drawviewmodel 1"
alias crossmodel2 "r_drawviewmodel 1"
alias crossmodel3 "r_drawviewmodel 1"
-----------------------------------------------------------------------------------
And thats it! Credit goes to "trog" for the stuff from the autoexec and "Loops :3" for his viewmodelscript (http://goo.gl/8OxKR) I used in the viewmod configs!

can you just bind it to a key like

bind n "toggle r_drawviewmodel 1 0" ?

aarons crosshair switcher. DABES

Then I would have to press "n" every time I switch to my melee weapon :/

I don't think crosshair switcher are toggleable

Do you really need lastused? Without replicating the "lastinv"-command it gets a lot easier.
German: Ich mein Du hast schon Mausrad und 1-3, wie oft wirst du dann mit q wechseln? Ohne das Ganze wirds etwas kürzer, ohne exec, zusätzliche cfgs und so weiter.

unbind "q"
unbind "KEY"
bind "KEY" "view"

alias viewoff "alias models "r_drawviewmodel 0"; alias view viewon"
alias viewon "alias models "r_drawviewmodel 1"; alias view viewoff"
viewoff

alias "s1" "slot1; models; bind MWHEELUP s3; bind MWHEELDOWN s2"
alias "s2" "slot2; models; bind MWHEELUP s1; bind MWHEELDOWN s3"
alias "s3" "slot3; r_drawviewmodel 1; bind MWHEELUP s2; bind MWHEELDOWN s1"

bind "1" "s1"
bind "2" "s2"
bind "3" "s3"

unbind "q"
unbind "KEY"
bind "KEY" "view"

alias viewoff "alias models "r_drawviewmodel 0"; alias view viewon"
alias viewon "alias models "r_drawviewmodel 1"; alias view viewoff"
viewoff

alias "s1" "slot1; models; bind MWHEELUP s3; bind MWHEELDOWN s2"
alias "s2" "slot2; models; bind MWHEELUP s1; bind MWHEELDOWN s3"
alias "s3" "slot3; r_drawviewmodel 1; bind MWHEELUP s2; bind MWHEELDOWN s1"

bind "1" "s1"
bind "2" "s2"
bind "3" "s3"

Lastused is one of my most used keys :/
German: Aus ner alten CS gewohnheit benutz ich leider den quickswitch sehr häufig um nicht zu sagen fast immer.

Then just keep using your script if the exec doesn´t cause lag.
German: Dann gehts nur wenig einfacher, lohnt sich meiner Meinung nach nicht das umzuschreiben, wenn es funktioniert.

Yeah, I'll try to improve it a bit though, some "bugs" are still there but I think this is the closest I can get. Thanks for the help!

I used Aron's crosshair switcher to set up my initial crosshairs, then I added in different interp values for each slot.

Then I copied each class config, make one use viewmodels on, and the other viewmodels off, and put them in a separate folder. Then in each of my class configs I added a bind so one key will exec the crosshair on config, and the other will exec the crosshair off config.

It's a complicated mess and a pain in the ass to edit, but I've barely had to make any changes to it since I set it up and it works for me.

Link: https://dl.dropbox.com/u/32621630/Crosshair%20Switcher.rar

i agree with mangachu
bind o "viewmodel_fov 0"
bind p "viewmodel_fov 120"

i find it really easy to use

I might try that.

bind 1 "slot1; r_drawviewmodel 0; viewmodel_fov 84"
bind 2 "slot2; r_drawviewmodel 0; viewmodel_fov .0001"
bind 3 "slot3; r_drawviewmodel 1; viewmodel_fov 84"

change for every class

thats not toggleable!

well bind the viewmodels to what you want and it theres not need for a toggle-able viewmodel script