Use one of the following entries with the spawn code:

Cyberdemon monster_boss_cyberdemon
Guardian monster_boss_guardian
Guardian's Seeker monster_boss_guardian_seeker
Sabaoth monster_boss_sabaoth
Vagary monster_boss_vagary
Archvile monster_demon_archvile
Cherub monster_demon_cherub
Hellknight monster_demon_hellknight
Imp monster_demon_imp
Maggot monster_demon_maggot
Mancubus monster_demon_mancubus
Pinky monster_demon_pinky
Revenant monster_demon_revenant
Tick monster_demon_tick
Trite monster_demon_trite
Wraith monster_demon_wraith
Cacodemon monster_flying_cacodemon
Lostsoul monster_flying_lostsoul
Zombie wth flashlight monster_zombie_ maint_flashlight
Flaming Zombie monster_zombie_bernie
Commando Zombie monster_zombie_commando
Commando Zombie with chaingun monster_zombie_commando_cgun
Fat Zombie with wrench monster_zombie_fat_wrench
Fat Zombie monster_zombie_fat2
Zombie in jumpsuit monster_zombie_jumpsuit
Zombie eating monster_zombie_jumpsuit_eating
Zombie in labcoat monster_zombie_labcoat
Zombie missing limb monster_zombie_limb
Zombie monster_zombie_maint
Bald zombie monster_zombie_maint_bald
Zombie with no jaw monster_zombie_maint_nojaw
Skinny zombie monster_zombie_maint_skinny
Zombie with Wrench monster_zombie_maint_wrench
Zombie monster_zombie_maint2
Zombie with a pipe monster_zombie_pipe
Chainsaw zombie monster_zombie_sawyer
Skinny zombie monster_zombie_skinny
Bloody mouthed zombie monster_zombie_suit_bloodymouth
Headless zombie monster_zombie_suit_neckstump
Skinny zombie in suit monster_zombie_suit_skinny
Bald Zombie in T-shirt monster_zombie_tshirt_bald
Zombie in T-shirt monster_zombie_tshirt_blown
Z-sec Zombie with machine gun monster_zsec_machinegun
Z-sec Zombie with pistol monster_zsec_pistol
Z-sec Zombie with shield monster_zsec_shield
Z-sec Zombie with shotgun monster_zsec_shotgun