Weapons and items:
Press ~ to display the console, then type give (item) using the following information. Other choices include give all, give weapons, or give ammo. 

ChainFist
ETF Rifle
Plasma Beam
Prox Launcher
Tesla
Double Damage
Hunter Sphere
Defender Sphere
Vengeance Sphere
A-M Bomb
IR Goggles
Doppleganger
Flechettes (ETF Rifle ammunition)
Prox (Prox Launcher ammunition) 


Level select:
Press ~ to display the console, then type map (level code) using the following information.

Name Level / code 
~~~~~~~~~~~~~~~~~~~~~~~
Single player 
Lower Mines RMINE1 
Mine Engineering RMINE2 
Thaelite Mines RLAVA1 
Tectonic Stabilizer RLAVA2 
Eastern Warehouse RWARE1 
Waterfront Storage RWARE2 
Logistics Complex RBASE1 
Tactical Command RBASE2 
Research Hangar RHANGAR1 
Maintenance Hangars RHANGAR2 
Waste Processing RSEWER1 
Waste Disposal RSEWER2 
Munitions Plant RAMMO1 
Ammo Depot RAMMO2 
Widow's Lair RBOSS 

Multi-player 
The Low Road RDM1 
The High Road RDM2 
Boxed In RDM3 
Razor Close RDM4 
Stone Hinge RDM5 
Nexus RDM6 
Sewer Citadel RDM7 
Styx and Stones RDM8 
Scenic Overlook RDM9 
Great Divide RDM10 
Dish It Out RDM11 
Fall From Grace RDM12 
Roads To Nowhere RDM13 
Rogue's Edge RDM14 

Other maps 
Weapon and ammo depot RUNIT2 
Weapon and ammo depot RUNIT3 
Weapon and ammo depot RUNIT4 

Fun kill :
Enable the give all code. Go to any level and get all the enemies to follow you. Run into a corner with them in front of you. Press [Tab] button until you see "AD bomb" or something similar, then press [Enter]. All the enemies must be in front of you. This will freeze all the enemies and allow you to walk around with no problems.