cl_weaponpreselect
When using the weapon command, this variable allows weapon preselection instead of standard immediate weapon selection. Preselection means that the preselected weapon will be switch right before +attack command, that is right before you shoot from your weapon.
Weapon preselection
Immediate weapon selection
Usefull in most teamplay games where you don't want to carry your best weapon in your hands but want to be ready to instantly shoot from it. Note: Doesn't work for impulse command, you have to use new weapon command.