NovaLogic programmed a good selection of cheats into the game, but in order to use them, you need to enable cheats. To do so, press NumPad 7.
Type in: IM A CHEATER and press enter. Cheats will be enabled. In order to use the cheats, again press NumPad 7, enter the cheat of your choice, and press enter. Bruce Campbell starts insulting and ridiculing you if you use them.

These are the cheats that NovaLogic programmed in to the game:

QUICKENING	Toggle God mode on/off.*
DILITHIUM	Restore all energy reserves to full.
COME GET SOME	Restores all ammo to full.
KESSEL RUN	Restores hull strength to full.
THERE IS NO SPOON	Instant mission win when you dock with starbase.
RAGTAG	All ships (GalSpan, Bora, and the Mako) owned.
BOOM STICK	All items available for purchase.
ONE MILLION DOLLARS	Adds 5000 credits to your account.
SAY AHH	Opens a targeted Tachyon Gate, if it is closed.

* With God mode active, you can still die from Radiation. (Go figure.)
BTW: Six of the above cheat codes are "borrowed" from movies and TV. If you can find all of them, and know what movies/shows they're borrowed from, you have no life. PS: I have no life.

These are things that were (probably) not meant to be a game cheat:

Nonstop Burning: If you need to get somewhere quickly, do a Burn (Tab key) and start holding the Slide (Q) key. You will continue traveling at your afterburner velocity, without using your burner energy. (Discovered by just about everyone; including myself)

Instant Recharge: Torpedoes are great, but they take a long time to fire. When you fire a torpedo, press the "Pause" key. Everything stops, but the torpedoes continue reloading. If you have Hunter torpedoes, holding down the fire button while quickly un-pausing and pausing again can let you get off a whole swarm of them almost simultaneously. You can usually hit an enemy at perfect straight to dead if you do this enough. (Discovered by me)

Instant Lock on: Guided weapons sometimes take a long time to lock on. However, if you start by facing your enemy, and cycle the weapon in (By pressing the 1 or 2 key) they will start by being locked on to your enemy. (Discovered by me)

Big Bucks FAST: Use the "Ragtag" cheat above and return to base. Go to "Shipyard" and sell the four most expensive ships. (IE, all but Orion) Hit "Back". Repeat as much as you want, before you re-launch, they'll just keep reappearing. (Discovered by me)

Disrupted Pirates: Sometimes Demon pirate fighters will be destroyed when you hit them with disruptor torpedoes. (Discovered by me; this is more of a bug than a cheat...)

Free Extra Missiles: If you put the ammo hold card in, then load up your missiles, then drop another card on top of the ammo hold, you can keep the extra missiles loaded. (Discovered by an anonymous tipster)