Use one of the following entries with the /item code.

weapon_fists
weapon_pistol
weapon_gausspistol
weapon_shotgun
weapon_minigun
weapon_mule
weapon_mechagun
weapon_beamgun
weapon_polarisblade
weapon_dml
weapon_chemgun
weapon_spchemicalgun
ammo_gaussclip
ammo_buckshot
ammo_minigunclip
ammo_beamgunclip
ammo_dmlclip
ammo_chemical
item_healthkit
item_armor
player_armor
vehicle_tank