Weapons and ammunition -
While playing a game, press ~ to display the console, then type one of the 
following codes:

give ionripper 
give phalanx 
give trap 
give mag slug 
give dualfire damage

Level select -
Press ~ to display the console, then type "map [level code]" using the 
following information to skip to the corresponding level:

Name - Level code 
The Swamps - xswamp 
Sewers - xsewer1 
Waste Sieve - xsewer2 
Outer Compound - xcompnd1 
Inner Compound - xcompnd2 
Core Reactor - xreactor 
The Warehouse - xware 
Intelligence center - xintell 
Industrial Facility - industry 
Outer Base - outbase 
Water Treatment Plant - w_treat 
Badlands - badlands 
Refinery - refinery 
Lower Hangars - xhangar1 
The Hangars - xhangar2 
Strogg Freighter - xship 
Cargo Bay - xmoon1