Planescape: Torment/Quests

Killing Carl Parfidor
In Curst, there is a quest given out by Roberta where she asks you to find an assassin that will kill her husband, Carl. Normally, this quest cannot be completed because the assassin, a hooker, will never spawn. However, the quest is fully coded and can be finished by spawning in the hooker via a mod, then continuing the quest as normal.

Elyce, her brother, and her boyfriend
There are script files for a scrapped quest that would've taken place in front of the Warehouse in the South-East Ward. When the player got near the Warehouse, a woman named Elyce would approach the player and ask them to stop her brother and boyfriend from attacking each other. From there, the player would have to approach the boyfriend and brother, whom are in front of the Warehouse, and either talk them into not fighting, goading them on, ignoring them or killing them yourself.

Pendant of Yemeth
A long and unused quest involving obtaining the Pendant of Yemeth can be found in the game's files. The quest starts with the player talking to an NPC named Ratbone in Ragpicker's Square. After talking to him for a bit and assuring him that no one has sent you, he'll tell you about a strange Collector that has a nobleman constantly with him. He'll then tell you that he saw an Erinyes, a female Battezu, talking to the Collector one night. After telling you this, he'll tell you to talk to some Battezu about this.

You can discuss Ratbone's information with the baatezu in the Smoldering Cavern. One of them will prompt the player to participate in a bargain with them once you've talked with Ratbone about the strange Collector. If the player agrees, they will tell the player about an Erinyes in the form of a Collector that has a pendant they want. She is located in the South-East portion of the Hive. However, she has a nobleman as her thrall that will fight you if you attempt to attack her. She will not have him with her in the evening, which gives the player a change to either bluff her into giving you the pendant or killing her for it. After getting it, you go back to the Battezu and get your reward, which is some sort of power from the pendant that doesn't work on you. At this point, you can either threaten to take the pendant back until you find a way for it to work, attack them, or leave them be.

There is some dialogue regarding you betraying them, but there doesn't seem to be anything in the Erinyes' dialogue that lets you do so.

Arkin's Ring
A scrapped quest involving a woman in the Buried Village looking for her father can be found in the game's files. The quest starts off by the player talking to her and her asking the player if they'd speak to a witch in town that have her father a portal ring that leads to a rare crypt for him to plunder. When the player talks to the witch, she reveals that she gave a portal ring to the girl's father, but didn't give him the way to exit the crypt, which is a purse. In order to find the location of the portal, the witch must get a human leg bone from the player. After the player gives her the bone, she'll point to a portal in the northwest. The player then explores the crypt and find the now-dead dad with a ring on one of his fingers. Once the player grabs the ring, the player returns to the woman and give her the ring, which ends the quest.

Forged Dead Contract
There is a scrapped quest that would let you pass off a Forged Dead Contract as the real thing so that you get the money for signing one, but don't have your body sold to them when you die. From what can be seen in the game's files, you would have to have the otherwise-worthless NPC Old Copper Eyes forge a Dead Contract for you, either for you or someone else. This was probably scrapped because signing a Dead Contract does nothing outside of giving you 50 coins.