During play, press ~ and type in the following codes:

megaboss          God mode 
satan             ""  ""
allit             All items and weapons
gimme all         ""  ""
.jt (#)           Skip to level (#). Refer to the following list:

Level                   Number 
First Steps              41 
The Outer Citadel        01 
Through the Citadel      30 
The Middle Castle        10 
In the Middle of         33
the Castle  
The Cathedral            11 
The Darker Cathedral     34 
The Cemetery             12 
The High Castle          13 
The Castle Cathedral     14 
The Factory              17 
The Machine Park         35 
The Train Station        07 
U-Boat Bunker            08 
U-Boat Pen               32 
V2 Factory               06 
City Ruins               09 
The Duel                 24 
The Time Machine         15 
The Future Time Machine  02 
Time Machine Facility    28 
Underground Channels     05 
The Sewers               31 
Kraftwerk                18 
Droid Factory            03 
Computing Center         19 
City in the Clouds       04 
The Spaceport            16 
Docking Bay 94           29 
The Flying Fortress      23 
 

Thanks to Revolution readers Jos Donkers, deros, Carlo van weeren and The Pod!