Arizona Killer

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

Quick walkthrough

 * Rendezvous with Cato Hostilius.
 * Infiltrate Hoover Dam and wait for the President to arrive.
 * Assassinate President Kimball.

Walkthrough
After receiving instructions from Caesar (or Lucius, if the former is dead), the player needs to meet Cato Hostilius, camped northwest of Ranger station Delta. When spoken to, he will present the player with a set of NCR armor and suggest planting a bomb on the Bear Force One (the player can receive such a bomb from him if their Explosives skill is at least 50). Afterwards, he 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 regulars and Rangers (the latter can see through faction disguises, making infiltrating the Dam whilst vilified by the NCR difficult). The player 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, leaving the location before completing the assassination or not arriving at the Dam at all will fail the quest.

Ten minutes after Cato is told that the player's 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. It will fail if the President leaves Hoover Dam in his aircraft alive or the player leaves the location without killing him. Note that failing this quest does not prevent the player from completing Render Unto Caesar.

Sabotage the Vertibird

 * 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 player passes an Explosives skill check of 50; it can also be pickpocketed from him. Accessing the helipad requires bypassing Jensen: the player can kill him silently, sneak past him, persuade him with a Speech skill check of 55, or dress as an NCR Engineer - there is an engineer's uniform in the supply closet inside the visitor center. Once planted, the bomb will explode when the Vertibird takes off.
 * Sabotage the Vertibird's flightplan: This is done using the computer terminal inside the visitor center, while the Vertibird is on the helipad. When the Vertibird takes off again with the President on board, it will crash, killing everyone on board. Note that all NCR characters turn hostile as a result.

Use explosives

 * Plant C-4 in Jeremy Watson's helmet: Jeremy Watson is an NCR trooper who is going to be decorated by the President. 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. 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.
 * Place C-4 near the President's route: C-4 explosives can be placed anywhere near the President's route to and from the helipad. The best location is the middle of the helipad (which requires bypassing Jensen), where it can be detonated to kill the President and his security detail when they step out of the Vertibird.
 * Create a human bomb: Requires planting several C-4 charges on Cato, Jeremy Watson, or any other NCR trooper who is close to the stage or the President's route. All of these can be later detonated simultaneously with a detonator.
 * Rig the anti-aircraft cannon to explode: This is done using the computer terminal at the top of the exterior staircase, just east of the visitor center doors. A Repair skill of 50 or more is required.

Applied violence

 * Program the anti-aircraft cannon to shoot down the Vertibird: This is done using the computer terminal at the top of the exterior staircase, just east of the visitor center door. A Science skill of 50 or more is required.
 * Shoot down the Vertibird with personal weapons: The Vertibird has a high damage threshold, and will require multiple shots from a powerful weapon such as the Gauss rifle or Tesla cannon (if the Vertibird is destroyed while President Kimball is not on board, the President will retreat into the visitor center and stay there with his guards, making it necessary to kill him personally).
 * The Dallas Method: Snipe the President using a long-range weapon. There are two notable locations: the top of the observation tower located on the rim of the Dam behind the stage (it is necessary to silently eliminate a Ranger sharpshooter on top of it first) and the base of the rocky ridge in front of the visitor center. Silenced long range weapons (such as a modified sniper or varmint rifle) are recommended.
 * The Sarajevo Method: Kill the President in close combat. Definitely the hardest option, as the area is populated by high level NCR troopers and Rangers with powerful weapons.
 * The Afghanistan Method: Use an area effect weapon (such as Fat Man or Euclid's C-Finder) to kill the President, his security detail and spectators.

Behind the scenes

 * A majority of this quest was implemented by Charlie Staples.

Bugs

 * If the player travels to the Fort, kill Caesar/Lucius and then returns to the Dam, President Kimball will be dead and characters neutral to the NCR will treat him as an assassin.
 * If the player kills the President at close range, the system will most likely overload and freeze up because of all the activity of the crowd and troops. The best way to avoid this is to kill the President at a distance using a Sniper Rifle or similar long-ranged weapon, then retreat from the area.
 * 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 player visits the Dam after recieving the quest but before making contact with Cato, the quest will automatically fail when he leaves the Dam area. If the player waits at the Dam without having met Cato, the President will never appear.