If you want to specify a key for direct (and faster) selection of a weapon, here is the command and the weapon names in the game (with "x" as a key you need to specify):

bind "x" "WEAPONNAME"

The "WEAPONNAME" for They Hunger are:

"weapon_th_spanner" = spanner "weapon_th_shovel" = shovel "weapon_crowbar" = umbrella "weapon_th_ap9" = semiautomatic pistol "weapon_th_sniper" = sniperrifle "weapon_th_chaingun" = chaingun "weapon_egon" = flamethrower" "weapon_th_medkit" = medkit

Those are the weapons you might wanna use in the game. Also have a look at this guide (which doesn't have the entirely correct names for all the weapons though) for better recognition of what those weapons are:

http://manke.blackwidowgames.com/th_walkthru/th_weapons.htm