Arizona Killer

Arizona Killer is a main quest in Fallout: New Vegas and an achievement/trophy for all platforms.

Synopsis
Aaron Kimball, President of the New California Republic, is making a visit to Hoover Dam to improve morale among his troops in the Mojave. His assassination would devastate NCR forces and inspire Caesar's armies.

Detailed walkthrough
After receiving instructions from Caesar (or Lucius, if Caesar is dead), the Courier must meet Cato Hostilius, camped northwest of Ranger Station Delta. Cato provides a set of NCR armor and suggests planting a bomb on the Bear Force One, which he will give to the Courier after passing a speech check (50 Explosives). Afterwards, Cato will make his way to Hoover Dam and blend into the crowd of spectators.

The entire area of the Dam is heavily guarded by combined patrols of NCR troopers and Rangers, who can see through faction disguises. The NCR will always be hostile when the disguise is discovered due to the failure of Don't Tread on the Bear! The Courier has a limited time to make some preparations before talking to Cato again in the crowd and telling him that they are ready. Waiting for too long (well over an hour of real time), leaving the location before completing the assassination, killing any ranger atop or in the immediate area of the visitor center (even quietly, this includes the trooper Jensen) or not arriving at the dam at all will fail the quest.

Immediately after Cato is told the Courier is ready, the Bear Force One will arrive and land on top of the visitor center. President Kimball will make his way to the stage to deliver a speech. If there is any suspicion that an assassination attempt is imminent, the Rangers will interrupt and hurry the President back to the Vertibird or a secured location beneath the helipad if the aircraft is inoperable. Otherwise, after the speech ends, the President and his security detail will simply leave. The President's death completes the quest, and if he successfully leaves the area, the Courier must report failure back to Caesar. If Colonel Moore has been killed at any point prior to starting this quest, it will fail immediately after being activated.

Skill check
In addition to the ability to assassinate Kimball using normal combat methods, there are several optional actions tied to specific skills.

Explosives

 * Plant a bomb on the Vertibird while it's on the helipad: Cato will provide the explosive necessary to blow up the Vertibird when it takes off, if the Courier passes an Explosives skill check of 50; it can also be pickpocketed from him. Accessing the helipad requires bypassing Jensen through stealth, persuade him with a Speech skill check of 50, or dressing as an NCR engineer (one is in the visitor center). Once planted, the bomb will explode when the Vertibird takes off.
 * Plant C-4 in Jeremy Watson's helmet: Jeremy Watson is an NCR trooper who is going to be decorated by Kimball. He is missing his helmet, which is on a table next to the stairs below the visitor center. Planting C-4 in the helmet requires an Explosives skill of 50 and a brick of C-4. Watson can then be pointed towards his missing helmet. When he retrieves it, he becomes a walking bomb that can be detonated when the President turns to decorate him. One will have to wait about 2 minutes into the President's speech.

Repair

 * Rig the anti-aircraft gun to explode: This is done using the console at the top of the exterior staircase (50 Repair), just east of the visitor center doors (next to a ham radio). The gun will explode just before Kimball calls up Jeremy Watson.

Science

 * Sabotage Bear Force One's flight computer: This is done using the computer terminal inside the visitor center (50 Science); the Vertibird does not have to be on the helipad. When the Vertibird lands, the program will be uploaded automatically. The Vertibird will crash into the Hoover Dam as a result.
 * Program the anti-aircraft gun to shoot down the Vertibird: This is done using the console at the top of the exterior staircase (50 Science), just east of the visitor center door (next to a ham radio). The gun will spin around and take out the aircraft before it gets over the dam.

Behind the scenes
A majority of the quest was implemented by Charles Staples.

Bugs

 * If the Courier travels to the Fort, kills Caesar/Lucius and then returns to the Dam, President Kimball will be dead and characters neutral to the NCR will treat them as an assassin.
 * Cato can spawn very close to the cazador nest, putting him in danger of death from the moment the quest begins. To avoid this, fast-travel to the area before taking the quest, clear out all the cazadores, and then go to the Fort to receive the quest.
 * If the Courier visits the Dam after receiving the quest but before making contact with Cato, the quest will automatically fail when he leaves the Dam area. If the Courier waits at the Dam without having met Cato, the President will never appear.
 * Sometimes the quest will fail immediately once started, forcing the Courier to report failure to Caesar. This usually happens if a specific male engineer stationed at the Dam has been killed prior to starting the quest, as he is a disguised Legion soldier. The death of this engineer sets a number of variables which set the NCR trooper guarding Kimball on alert, thus automatically failing the quest once it is taken.
 * Occasionally, Kimball's Vertibird never arrives at the Dam, making this quest impossible to complete without the use of console commands. Can occur when reloading saves during the mission.