There are two special ones I remember getting outside of the Gladiator Pit and Greyfold story.
Aluminum Fever is found by going to the Greyfold Pawn Shop with high inteligence and finding a box of broken gun parts. You repair it and get a unique gun.
Blood is Thicker is found by equipping a gas mask and having unglow pills. Spam search the Bomb Pit in Greyfold until you find a steel door. Password is 810674, it was on that train when you get attacked by a snake. You can also just use strength if it's 10 or intelligence if it's 8. Search it for canned tuna and gunpowder. It'll show a prompt to search a sealed door, open it and a grenade will blow up, dealing around 150 damage. If you live, you get a unique tommygun.
Also all the stuff from giving the book to Bedivere after changing the ending of the book.