In Console Type sv_cheats 1 Then In Console Type god Then In Console Type impulse 101 , And notarget , And noclip and npc_create npc_headcrab
npc_create npc_metropolice npc_create npc_combine_s buddha

npc_create npc_zombie
npc_create npc_alyx npc_create npc_citizen npc_create_equipment weapon_ar2