Thundergun

"So this is what Maxis was keeping secret!"

- Edward Richtofen

The Thundergun is a powerful  Wonder Weapon featured in Zombies and can also be found via an easter egg in the campaign mission "Numbers". It appears on the zombie maps Kino der Toten, Ascension, and the Call of Duty: Black Ops edition of Nacht der Untoten.

Overview
The Thundergun is a large, cannon-shaped weapon that fires blasts of incredibly strong compressed air. It has no iron sights, meaning it must be fired from the hip. It is able to kill large numbers of zombies with a single shot, sending them flying backwards or up. Those who are not killed by the blast are thrown backwards and will remain on the ground for a few seconds before getting back up. The Thundergun holds two rounds in its magazine, and has twelve rounds in reserve. The Thundergun can only be reloaded when all shots have been fired. The Thundergun is important during the later rounds as it is useful for clearing large groups of zombies in order to reach a downed teammate or make an escape. It is extremely useful when swarmed because it will easily kill a large group of zombies in one shot.

It is often used as a reserve weapon, as it has a low amount of ammunition and a moderately slow reload. It can only be reloaded when the entire magazine is empty, except in the campaign mission "Numbers", where one can execute a partial reload. Because of this, it is advised to shoot any extra rounds in a magazine before obtaining a Max Ammo. Wasting ammo on one zombie or a small group is not advisable. It is also a decent weapon against Hellhounds as it can easily take large numbers of them out and will always kill them in one hit, with there also being a Max Ammo at the end of a Hellhound round.

Campaign
The Thundergun can be found and used in the campaign level "Numbers" as an easter egg, similar to the Ray Gun in "Little Resistance".

The Thundergun found in "Numbers" comes with two shots in the magazine and 12 shots in reserve. However, unlike in Zombies, it is possible to reload without the entire magazine being empty. It also gains a full ammunition refill after sliding down the pipe and at the second weapons cache. Because of this, it becomes very useful when playing on Veteran. In essence, it works much like an extremely powerful shotgun, throwing and almost always instantly killing anyone caught in its massive spread, often with enough force to tear off limbs.

The player can swap out for another weapon, and the player will be able to pick it back up. Sometimes after picking up another weapon, however, the Thundergun becomes unusable because of a bug.

The steps and video on how to do it are shown below:

337px|right|CoD: Black Ops - Thunder Gun Easter Egg
 * 1) After the interrogation scene ends there are six big white canisters in front of the player on the walls. (Note: they are not the small propane tanks on the ground; they are the big white ones).
 * 2) Shoot, or throw grenades at all six canisters until Nova-6 comes out (note: the player must cause damage to the canisters before the enemies do, so the player might want to flashbang the enemies to prevent them shooting the canisters).
 * 3) Run past the ladder to a small room connected to where the player first starts the mission.
 * 4) If done correctly the player will see a black tape sticking out of a cassette player next to the door way.
 * 5) Hold down the action key and the tape will disappear from the cassette player, or the obvious shake in the screen as cue.
 * 6) Continue on until the player gets to the first of Clarke's weapon caches, behind the fridge after the rooftop jump.
 * 7) Look to the left and the player should find a cassette player.
 * 8) When at the cassette player, press the use button and the cassette will go in.
 * 9) If done correctly, notice the tape goes in and the player hears several tunes, and the screen shakes.
 * 10) The Thundergun will appear on the wall above the cassette player.

Zombies
The Thundergun can be obtained through the Mystery Box for 950 points in the maps Kino der Toten and Ascension, and the revamped Call of Duty: World at War map Nacht der Untoten. It shoots a compressed air shock-wave blast that knocks any zombies backwards that survive the original hit. It is not advised to upgrade it until out of ammo.

When Pack-A-Punched, it becomes the "Zeus Cannon". The Zeus Cannon's magazine capacity is increased to 4, and its reserve capacity is increased to 24, effectively acting as double ammo. It has increased range and radius, and can now knock over zombies off-screen.

The Thundergun is one of the most useful weapons in Zombies Mode, especially when another player is downed. It can clear huge amounts of the undead with minimum effort, which can help the player reach the downed player extremely easily. It can kill multiple zombies without hassle and can save the player's life, but the downside is its short range. Despite being unusable, the Thundergun also makes an appearance in "Five" in the weapons-testing lab, suggesting that the Thundergun was found by the United States and was being reverse engineered by the Pentagon.

It is debatable whether or not the Thundergun is better than the Wunderwaffe DG-2. The Thundergun will kill all the zombies within its range and, unlike the Wunderwaffe, it does not hurt the player when fired close-range. However, the Wunderwaffe can kill zombies which would normally be out of the Thundergun's blast range, and has the ability to kill zombies around corners. The Thundergun also has less ammo overall, and cannot be reloaded without unloading the magazine, unlike the Wunderwaffe. It is, for all intents and purposes, impossible to miss with the Thundergun if the Zombies are within its range, whereas missing with the Wunderwaffe is certainly possible.

Creation
The Thundergun was originally thought by Richtofen to have been created by Dr. Maxis and that Maxis had been deliberately hiding it from him as he grew to not trust Richtofen, although this could mean that Richtofen didn't trust Maxis and became paranoid. Richtofen even referred to it as the DG-3 (meaning he considered it to be the Wunderwaffe DG-2's successor). However, one of the radios in Ascension reveals the true creation of the Thundergun. It was a Russian weapon codenamed "Project Thunder" and was being worked on by the Ascension Group under Gersch's direction. Gersch knew about its range problem and was trying to fix it. He also knew about its small ammo (power cell) count.

Trivia

 * For some reason, sometimes it is possible to reload the Thundergun mid-magazine in Zombies.
 * Richtofen is seen holding the Thunder Gun on the Ascension poster.
 * The Thundergun is the only gun in Zombies that cannot reload mid-magazine.
 * In Zombie mode while a single kill with the Thundergun gives the player 50 points, each additional kill provides less points and the total amount can not exceed a total of 300, meaning that killing 24 zombies will still add 300 points to the players score.
 * The sound heard when receiving the Thundergun in "Numbers" come from transmissions of GKNOVA6.
 * The gun has "Osterezheniye" written on its side, which is the misspelled Russian word for "Warning", which correctly spelled is "Предострежение" (Predostrezhenie).
 * The two red glowing lights on the front of the canister when loaded into the gun indicate how many shots are left in the magazine. When upgraded there are three lights visible as one of them is hidden by other parts of the gun. This is fixed on the IOS version of the game.
 * If zombies that are knocked down by the Thundergun's blast are attacked by players, they will instantly be back up on their feet, instead of slowly rising up.
 * If the player kills an enemy with the Thundergun on Numbers, the enemy might groan like a zombie.
 * The Thundergun and the Ray Gun are the only Wonder Weapons that can be found in Campaign.
 * However, only the Thundergun has its own pick up icon, as the Ray Gun reuses the M1911's.
 * Despite appearing only once, the Thundergun's pick-up icon is actually very detailed.
 * The Thundergun deals no friendly fire damage in "Numbers".
 * There is an unusable Thundergun in a metal locker in "Five". It is in the same room as the unusable Winter's Howl and Death Machine.
 * If the player turns off rag doll effects, zombies will not fly backwards when shot; they just fall as if they were taken out by conventional weapons.
 * Occasionally, Zombies caught at close range in the blast will not be affected at all, as if the weapon missed them entirely.
 * "Stainless Steel" can be seen written on the Thundergun.
 * The Thundergun was originally going to be a usable weapon on "Five", as there are quotes in the games files for each character, as can be seen here
 * The reload sound of the Thundergun in third person is that of the Crossbow.
 * The Thundergun in "Numbers" can be reloaded mid-magazine.
 * When the Thundergun in "Numbers" is reloaded mid-magazine, the current magazine will disappear and the empty reload is executed, as the Thundergun has no mid-magazine reload.
 * It is also noticed that the red lights that indicates the number of bursts will float in the air when reloaded mid-magazine.
 * Zombies killed by the Thundergun will not drop power-ups.
 * The Zeus Cannon's wind shot looks slightly purple on the inside.
 * Despite the fact that there is a foregrip on the gun, the third-person model doesn't use it.
 * An ad for the Thundergun can be seen on the loading screen for Moon.
 * The Thundergun has visible iron sights, although the ability to use them was never featured in the game.
 * In the Wii Version of Call Of Duty: Black Ops, if the player obtains the Thundergun from the Mystery Box, he/she will notice that there is no orange/red glow on the Thundergun.
 * According to the game's files, the Thundergun was originally going to appear in Black Ops II as a wall weapon.