Enter the options menu, select "Controls", then "Advanced". Turn on the option for the console. Then press ~ during game play to display the console window. Type sv_cheats 1 to enable cheat mode.

Code	Effect
change_portalgun_linkage_id < 0-3 >	Allow separate sets of portals to be created
upgrade_portalgun	Allow use of second portal placement
fire_energy_ball	Fire an energy ball
sv_portal_placement_never_bump 1	Portal placement cannot be bumped
sv_portal_placement_never_fail 1	Portals can be placed on almost any surface
ent_create_portal_weight_box	Spawn Weighted Storage Cube