All Super Arcade Modes: 

The Experimental PQZ ship: Type 'TECHNO' at the Tyrian 2000 main menu.
TX Silvercloud: Type 'UNKNOWN' at the Tyrian 2000 main menu.
Stormwind - The Elemental: Type 'STORMWIND' at the Tyrian 2000 main menu.
Ninja Star: Type 'STEALTH' at the Tyrian 2000 main menu.
Foodship Nine: Type 'WEIRD' at the Tyrian 2000 main menu.
Dragon: Type 'LIZARD' at the Tyrian 2000 main menu.
Captured U-fighter: Type 'ENEMY' at the Tyrian 2000 main menu.
Pretzel Pete Truck: Type 'PRETZEL' at the Tyrian 2000 main menu.
Nort-Ship Z: Type 'NORTSHIPZ' at the Tyrian 2000 main menu. 

Hidden difficulties: 
On the difficulty selection menu, press 'SHIFT' and 'G' together to 
open the Impossible setting. 

After entering the code for Impossible setting on the difficulty selection
menu, press 'SHIFT' and ']' to open Suicide setting. 

Super Tyrian mode: 
At the Tyrian 2000 main menu, type 'ENGAGE' for Super Tyrian mode 
Lord of the Game difficulty. 

For Super Tyrian mode on Suicide difficulty, hold the Scroll Lock key 
and type 'ENGAGE' at the Tyrian 2000 main menu. 

Debug mode: 
During a level, press 'BACKSPACE' and 'F10' to enter/exit debug mode. 

Invulnerability: 
During a level, press 'F2' + 'F3' + 'F6' together. If the message "Cheaters 
always prosper" appears, you've entered the code correctly. You can 
lose all of your armor, but you will not die
until you deactivate the code (by pushing 'F2' + 'F3' + 'F6' together again). 

Random Color Change: 
During a level, press 'BACKSPACE' and '-' to randomly change the 
board's color scheme. 

Random Song: 
During a level, press 'BACKSPACE' and 'SCROLL LOCK' to randomly
change the background music. 

Christmas mode: 
From the Start-Programs menu, select "MS-DOS Prompt". A DOSshell 
window will appear. Change to the Tyrian 2000 folder. Type "file0001 
yesxmas" and press the 'Y' key when prompted. Certain items, weapons, 
ships and sound effects will be changed to reflect the holiday spirit. 

Destruct Mini-game: 
Type 'DESTRUCT' at the Tyrian 2000 main menu to access the Destruct 
mini-game. 

There are five modes to play:
5-Card War (5 units vs 5 units)
Traditional (one on one battle)
Heli Assault (4 helicopters vs 8 ground units)
Heli Defense (8 ground units vs 4 helicopters)
Outgunned (green troops outnumbered by opponent's units)
Press 'F1' for the list of controls. 

Instantly end level: 
During any level, press 'F2' + 'F6' + 'F7' to instantly warp off of the level. 
Please note that this will not work with any Super Arcade ship nor will it 
work in Super Tyrian mode. 

"Super" Pause: 
During a game, press 'Backspace' and 'Number Lock' together. After doing 
this, you will not see the word "Pause" on the screen when you pause the game (by pressing 'P'). 

Wild Detail mode: 
Run the Tyrian 2000 setup program. Highlight "Game Detail" and press the 'W' key.