Here is some Half-Life 2 Console Commands.

give: A command that gives you items you want.

Give commands:

weapon_crowbar
weapon_physcannon
weapon_stunstick - You can't use them as a weapon, but pick them up for armor.
weapon_pistol
weapon_357
weapon_smg1
weapon_annabelle - which Father Grigori uses to battle zombies in Ravenholm.
weapon_shotgun
weapon_frag
weapon_alyxgun
item_suit
item_box_srounds - Spawns ammo box for Pistol
item_box_mrounds - Spawns ammo box for SMG
item_box_buckshot - Spawns ammo box for Shotgun

Impulse cheats:

impulse 101 - Gives you all the weapons and gives an HEV suit. Except for Annabelle
impulse 82 - Spawns a Jeep with Laser Cannon and SMG ammo box. Use Gravity Gun when stuck.

NPC Cheats:

npc_create - Command to spawn NPC where you are aiming at.

npc_create commands:

npc_alyx
npc_breen
npc_barney
npc_cscanner
npc_metropolice
npc_monk - Spawns Father Grigori
npc_combine_s
npc_dog
npc_eli
npc_mossman
npc_gman
npc_zombie
npc_fastzombie
npc_poisonzombie

npc_create_equipment - Spawn NPC's with a weapon

npc_create_equipment commands:

weapon_physcannon
weapon_stunstick - NPC's can use this.
weapon_pistol
weapon_357
weapon_smg1
weapon_annabelle - which Father Grigori uses to battle zombies in Ravenholm. But damages high.
weapon_shotgun
weapon_frag
weapon_alyxgun

Also, here is the command to kill G Man in Point Insertion.

ent_fire gman ignite

Those are all the cheats I have to say. If you need help, PM me.

Take a look at the picture, you see no G Man.