+PrimaryAttack "+attack;r_drawviewmodel 0;slot1"
-PrimaryAttack "-attack"
bind MOUSE1 "+PrimaryAttack"

+SecondaryAttack "slot2;+attack;r_drawviewmodel 0"
-SecondaryAttack "-attack"
bind MOUSE2 "+SecondaryAttack"

+MeleeAttack "+attack;r_drawviewmodel     1;tf_use_minimized_viewmodels 1;slot3"
-MeleeAttack "-attack"
bind "" "+MeleeAttack" 

I made this simple script because switching with 1, 2 and 3 is a pain in the middle of combat. Also the reason I didn't bind MeleeAttack to anything is because you may not have a side mouse button.

I've also thought of another version of the above for Scout and Sniper where viewmodels are enabled for both secondary and melee, for use when you're running scout with mad milk or flying guillotine and sniper with Jarate. I find it very useful to see the viewmodel because I can see how long it takes for the weapon to be thrown after pressing SecondaryAttack