Press "Ctrl, Alt and ~" to bring up the console and type in the following and then press "Enter" when done to spawn one of the following. Each one mess be entered seperatley. There is a bigger list but these are the only ones that work! If you don't want to ruin the game and see some of the future enemies in game then don't use these or even read this list! If I have a "unknown enemy" listed that means I just don't know what it is called.

Effect	Code
Spawns "Spider" mechs (Massive)	spawn monster_harvester_combat
Spawns a doctor	spawn char_doctor
Spawns a marine (has a gun)	spawn char_marine
Spawns a marine in shirt and shorts	spawn char_marine_fatigues
Spawns a marine that fixes armor	spawn char_marine_tech_armed
Spawns a Medic marine that heals you	spawn char_marine_medic
Spawns a Repair Bot	spawn monster_repair_bot
Spawns an unarmed, unnamed techy.	spawn char_marine_tech
Spawns an unnamed, armed medic.	spawn char_marine_medic_armed
Spawns Boss (Very Big)	spawn monster_makron
Spawns enemy with Shield	spawn monster_gladiator
Spawns Fatty Boss (Big and Invincible)	spawn monster_fatty
Spawns Kane in Strogg form (has a gun)	spawn char_kane_strogg
Spawns Mech Boss (Small)	spawn monster_bossbuddy
Spawns the Network Boss (Big)	spawn monster_network_guardian