The Superhuman Gambit

The Superhuman Gambit is a Fallout 3 side quest. It is also an Xbox 360/PC achievement and PlayStation 3 trophy.

Detailed walkthrough
The town of Canterbury Commons has become the battleground of a "supervillain"—the AntAgonizer and a "superhero"—the Mechanist. Its inhabitants are not very happy about it (save for Derek Pacion) and ask the Lone Wanderer if they can help them.

Upon arriving in Canterbury Commons, the AntAgonizer and the Mechanist will be engaged in a standoff. After a few scripted opening semantics, the two will engage in a brawl. Once the dust clears, both will run away, and Uncle Roe will speak to the player character, asking them to handle the ordeal. With a speech check, One can ask for double the pay, from 200 to 400 caps. After accepting the quest, speak to Derek Pacion. He provides the best info on where to find them. The AntAgonizer lives in a cave north of town and the Mechanist lives south of town in an old robot factory. (Both locations will be marked on the map.) With the Child at Heart perk, one can ask Derek for their weaknesses. The Mechanist does not harm the innocent, and other than the royal guard, the AntAgonizer's ants are weak. He will also comment that one should become a superhero named "Awesome-Claw", and suggest leading an army of deathclaws against them. He may alternatively tell the player character that they should be called "Super Humongous" and command a group of super mutants to do their bidding. He may also call the player character "Shadow Bite," or the "Brilliant Shadow," commanding an army of mole rats. There are several other names he may suggest, such as "The Lucky Guy" depending on high skills or S.P.E.C.I.A.L. stats.

AntAgonizer's Lair
If one decides to take out the AntAgonizer, head to the AntAgonizer's lair north of town. Go down all three sets of stairs and enter the first room to the right after the bend in the hallway. A button on the wall opposite of the entryway lowers a staircase to a cave. Continue through the cave to the AntAgonizer's lair.

Alternatively, sneak in the back entrance - a pipe to the west of the entrance at the top of the same mountain of rocks that the main entrance is on (requires a lockpick skill of 50). This route bypasses all of the ants in the tunnels. It is also possible to use this entrance if one has pickpocketed the AntAgonizer's key during the brawl when first entering town.

Once in her lair, there are no ants to fight, just the AntAgonizer. There are several ways to interact with her at this point:
 * If one has already received the The Mechanist's costume and are wearing it, she will attack along with her ants after a brief introduction, believing the player character to be the Mechanist.
 * If one has the Mechanist's costume but are not wearing it, there is the option of giving it to her. Giving it to her will award one with the Ant's Sting, a knife that poisons an enemy for an additional 4 damage per second for 10 seconds, and negative Karma (as she remains a delusional "supervillain").
 * By attacking her or speaking with her and being aggressive, one can engage her in battle. Killing the AntAgonizer will not affect Karma even though she is an evil character.
 * Speaking with her, one can choose to help her destroy the Mechanist. The Mechanist will barge into her lair and will have to be fought.
 * If one chooses to tell her the suit is not worth her attention, she will agree, and then prepare to leave the town. Though it may seem a good deed, one will still receive negative karma for choosing this option.
 * If one has learned the true name of the AntAgonizer from Joe Porter (by speaking to him and passing a speech check), she may be convinced to see the error of her ways. Having the Lady Killer perk guarantees success in this endeavor. She will then give up her career as a supervillain and hand over her costume before leaving quietly.
 * If one has been to Hubris Comics and have read the note to the editor concerning the AntAgonizer's canceled Grognak the Barbarian comic, this information can be used to point out that she can still be redeemed. Doing so will yield good Karma. This bypasses the gender-specific perk and skips the very tough speech check. She will also still hand over her costume.

Mechanist's Forge
The Mechanist's Forge is located just south of town on higher ground, inside the Robot Repair Center.

To reach his hideout without having to fight through his robotic security, one can lockpick the elevator in the hallway across from the entrance, bypassing the heavily guarded stairs. This requires a skill of 75 or above. Otherwise, the facility is broken up into four sections: Office (left of the entrance), two Maintenance areas (Sector A and B, which are connected by a control room on the upper level) and the Mechanist's Forge which allows entrance to the Mechanist's lair via the coffee maker. Sector B is closest to the entrance (metal door past the elevator), and the Forge entrance is on the upper level of Sector A, where activation of the coffee maker accesses the hideout. If accessing via the elevator, the coffee maker will not need to be activated, as it is on the other side of the corrugated door seen in the Mechanist's lair. This can be confusing as the entrance from the elevator, and the entrance from the upper level are both called Mechanist's Forge.

The security terminal for Sector B is in the control room on the upper level, which allows one to disable the automatic turrets and security robots. The security terminal for Sector A is located in a small control room near the back of the bay, close to the Forge entrance (upper level). From this terminal, one can disable the automatic turrets in this room, as well as emit an emergency pulse explosion that will destroy any active robots in this sector.

If the AntAngonizer has been killed earlier, one will need a lockpick skill of 75 to open the Mechanist's lair.

Enter the forge and activate the coffee maker to reveal the Mechanist's lair. Activate one of the little gears to the right of the door.

Once in the Mechanist's lair, there are several options that echo the interactions with the AntAgonizer:
 * If the player character is wearing the AntAgonizer's costume, he will believe them to be her and attack.
 * If the player character is not wearing the AntAgonizer's costume but have it in their possession, they may give the costume to the Mechanist. The Mechanist will give the player character Protectron's Gaze, a laser pistol that fires bursts of laser beams like, and one will receive negative Karma (as he remains a delusional "superhero"). It cannot be obtained by killing him; his body only holds a normal laser pistol when looted.
 * Attacking the Mechanist or using threatening speech will, of course, result in the Mechanist turning hostile. Killing the Mechanist does not result in negative Karma.
 * If one chooses to help him defeat the AntAgonizer, he will say something about her attacking the forge. One will then have to follow the Mechanist and help him defeat her and her ants.
 * Convincing the Mechanist to end his superhero career and leave the town alone will grant the player character his suit and positive Karma (like with the AntAgonizer, it is a very difficult speech check).
 * Either the Black Widow or the Child at Heart perks give a dialogue option to tell him he is scaring the whole town. With that, he will hand over his suit and leave (With both perks, only the Black Widow dialogue choice will be available). This also results in positive Karma while allowing one to bypass the speech check.

Rewards
OR OR
 * 200 caps (Stopping one of them)
 * 400 caps (Stopping both, or asking with the Speech skill to be paid 400 and stop one)
 * 600 caps (Stopping both after asking for 400 caps with the Speech skill)

Bugs

 * If one walks into Canterbury Commons from the north and enter Dominic and Machete's house first, the player character will not see the fight between the AntAgonizer and the Mechanist, yet Roe and everyone in town will act as if they did.
 * If one does not stay to watch the event between the AntAgonizer and the Mechanist, and then immediately speak to Uncle Roe, all three characters may disappear. If this occurs, the quest cannot be finished.
 * Upon first coming to Canterbury Commons and seeing the Mechanist and the AntAngonizer fighting and target the ants, they will have no name.
 * The AntAgonizer's health sometimes will not decrease despite being hit numerous times—this occurs even in her lair. The only known fix is to continue hitting her until she randomly dies.
 * Reverse-pickpocketing a suit from either the Mechanist or AntAgonizer and giving it to the opposing party will update the quest status to "Report back to town for your reward" (as should normally happen). However, speaking to Uncle Roe will not reveal the normal dialogue choice to end the quest and receive your reward. This can be circumvented by killing either the Mechanist or the AntAgonizer, or both.
 * Upon teaming up with the Mechanist and having to defend the Forge, he may wander off and disappear. When one talks to Uncle Roe after killing the AntAgonizer, the Mechanist will have died; therefore, the Protectron's Gaze cannot be acquired.
 * After convincing the AntAgonizer to leave, she will travel to Megaton. If one has blown up Megaton before this quest, she will enter through a door inaccessible to the player character, making the optional objective to kill her is impossible to complete.
 * Sometimes the Mechanist's sentry bot will stay in the same position for the rest of the game.
 * If one has passed the speech check with The Mechanist and the turrets in sector A have been turned off instead of destroyed, they will become hostile towards The Mechanist and kill him. If one reaches the terminal before/after they kill him, it will show the turrets as still being disabled.
 * If either of the two robots the Mechanist controls in the encounter the player character witnesses on arrival is killed, they may be replaced randomly at a later date by two functional robots, possibly different types. These new robots will be friendly to both the player character and the town and will attack enemies who enter. They will remain at the entrance to the town.
 * If one manages to somehow obtain both the ant's sting and the Protectron's Gaze before speaking to Derek Pacion, the only way to finish the quest is to kill either the AntAgonizer or the Mechanist, then speak to Uncle Roe. One cannot obtain the 600 caps because of this.