Infinite Ammo
Enter the following password into the cheat menu to unlock: MADMAN
Invisibility
Enter the following password into the cheat menu to unlock: SLLEWGH
All Weapons
Enter the following password into the cheat menu to unlock: TEXAS
Unlock All Levels
Enter the following password into the cheat menu to unlock: SELLOUT
Invincibility
Enter the following password into the cheat menu to unlock: EMERPUS
Unlock Everything
Enter the following password into the cheat menu to unlock: FMNFB
See-Thru Dinosaurs
After you kill a dinosaur and it is laying on the ground, kneel next to it and walk into it. If you do this before the dinosaur disappears, you will be inside the dinosaurs body. You can go into the tail, the middle, or the head. (Note: this also works with large un-dead dinosaurs.)
Bonus Level
Go to the cheats menu and enter ZOO. You shall now be able to go to a zoo and practise killing dinosaurs which don't attack you.