Cheat Codes 

Type these codes in at the code entry screen

NODIE                                     invincibility
GIMME                                     all weapon
FREEPLAY                                level select
NOSEEUM                                invisibility
THDOTEST                              test mode
IMHUGE                                   huge mode
SHORTY                                  short mode

Level Passwords

Type these passwords in at the code entry screen

BOOTCAMP                              bootcamp
DINNER                                    dinner table
OVERPASS                               bridge
COOLER                                   refrigerator
NECROPOLIS                            graveyard
CITADEL                                  castle
MOUSE                                    tan base
ESCAPE                                    revenge
ESCRITOIRE                              desk
COT                                         bed
BLUEBLUES                               plasticville
BUYME                                     toy shelf
EXPRESS                                   cashier
LITTLEPEOPLE                           toy train town
NUKEM                                      rocket base
EIGHTBALL                                pool table
BLACKKNIGHT                            pinball machine

(Thanks to capplin@msn.com)