If you use any cheats when playing, when you complete the game, a big "CHEATED!" will
be displayed. You must use a save game that has no cheats to complete the game
without the announcement.
Half-Life 2 Weapons
Go into console (~) and type impulse 101
(make sure sv_cheats 1 is enabled).
Shoot Portal Anywhere
Enter sv_portal_no_fail 1 in the command box
it does not work on layers of non flat land.
Bring up the command bar and enter npc_create npc_ then for the npc name like gman or headcrab or even zombie.
Fly Through Walls
After doing the sv_cheats 1 thing, press ` (~) to open the console and type: "noclip" and you will fly through walls.
After enabling cheats, type: "notarget" and enemies won't see you.
First, enable cheats. Then type "god" and you can't die anymore.
How To Get Weapons From Half Life And Max Portal Gun
If you have already done the sv_cheats 1 cheat, then type: "impulse 101" and you will get the weapons from half life.
You first have to activate the console. Then press ` to open it. Then type: "sv_cheats 1" and the game will allow cheats.