hud_fastswitch

hud_fastswitch
is a console variable available in all Source games.
If true/set to 1, disable the weapon menu on the top of the HUD, and switch directly to a weapon without waiting for +attack (default MOUSE1) "confirmation".
If set to 2, console weapon selection HUD is used.
If set to 3, horizontal scrolling weapon selection HUD is used (default on Postal III).