Press ~ to display the console, then type give using the following information. Other choices include give weapons, give all, 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)

To unlock the following levels, press ~ to display the console, then type map using the corresponding codes:

Single player
LEVEL - CHEAT CODE
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
LEVEL - CHEAT CODE
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
LEVEL - CHEAT CODE
Weapon and ammo depot - runit2
Weapon and ammo depot - runit3
Weapon and ammo depot - runit4

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.