During gameplay press the '~' (tilde) key to display the console window then type one of the following codes and press 'Enter' to enable the corresponding effect.

Toggle God Mode:
Set god (0 or 1)

Refill Current Weapon's Ammunition:
Ammo

Removes NPCs from Map:
Clear-npcs

Set Water Level; 0 is Default:
Flood (number)

Extra Upgrade Points for Guns:
Guns.points (number)

Spawn Blue Aura Characters:
Specialize

Toggle Invisible to Enemies:
Set player.ghost (0 or 1)

Toggle Turrets from Overheating:
Set gun.heat.rate (0 or 1)

Toggle NPC Muzzle Flash:
Set npc.gunlights (0 or 1)

Set Gunslots to carry more Guns:
Set player.gunslots (number)

Set Melee Range; 10,000 is unlimited:
Set melee.reach (number)

Set Friction:
Set player.frictionHL (number)

Toggle Smoke and effects when NPCs fire Guns:
Set npc.gunparticles (0 or 1)

Set Gravity; -32.15 is default, larger values allow higher Jumps:
Set phys.gravity.y (number)

Set Walk Speed; 18 is default, higher values increase Speed:
Set player.speed (number)

Toggle Attacking your Allies except for Dexter and important Characters:
Set player.friendlyfire (0 or 1)