Spectre 9mm: A basic semi-automatic pistol chambered in 9mm. 20 round ammo capacity. Low recoil makes for a fairly accurate weapon. The weapon also reloads quickly. It is one of the four starting weapons in Pro.
UDP 10mm: Semi-automatic handgun firing 10mm rounds. While it has more recoil, the weapon fires stronger shots than the Spectre 9mm. Of course, due to the size of the round, its ammo capacity is less than the Spectre's at 12 rounds, but reloads just as quickly. It is unlocked in Pro by collecting the Gun Parts in the Blank Canvas.
Model 6-357: A six-shot snubnosed revolver chambered in .357 Magnum, as indicated by the name. It reloads at a fairly quick rate. The weapon can also kill with two shots to the head, or three to the body. It is one of the four starting weapons in Pro, alongside the Spectre 9mm, PDW-9, and M1370PG.
Model 5-454: Another snubnosed revolver, this one uses the .454 Casull round. Of course, as the name signifies, it has a load capacity of 5 rounds in its cylinder. Strong enough to kill in one shot, especially to the head. Reloads a little quicker than the Model 6-357. Speaking of which, you can unlock the Model 5-454 in Pro by getting 50 kills with the Model 6-357 in the Cryogenics Lab.
SS-500: The strongest of all revolvers in the game, chambered in the extremely powerful .500 S&W Magnum. Its shots are strong enough to punch through two enemies at one time, making it good for accumulating headshots. Due to the lengthened barrel, it is heavier to hold, but is more accurate. Holds four rounds before needing to reload. Has the quickest reload time of any of the revolvers, but is also the slowest-firing. It can be unlocked in Pro by completing every objective in a single round in the Basement. The Murder Snub and Hyper Death Blaster are also unlocked when you acquire this weapon.
Murder Snub: A snubnosed revolver chambered in .357 Magnum, and one of the two gag weapons in the game. 5 round capacity. Once all five rounds are spent, the revolver is then disposed of and another takes its place pre-loaded. In Pro, It can be unlocked along with the SS-500 and Hyper Death Blaster by completing every objective in one round in the Basement.
M1370: A pump-action shotgun that has a stock, and a capacity of four shotshells. Like any shotgun, it's potential is realized when used at close range. Unlocked by collecting the Gun Parts in the Hydroponic Garden in Pro.
M1370PG: A stockless variant of the M1370 with the load capacity extended to five shotshells. Easier to aim, but reloads slower than the base model. It is one of the four starting weapons in Pro.
Il Duce: A break-action over/under shotgun with a 2 round loading capabity. The best part of this weapon, is that it can fire off both shells at once, unleashing more pellets and a wider spread. Useful for gibbing enemies at close range. To unlock this weapon, you must complete every task in a single round in the Hydroponic Garden in Pro.
PDW-9: A submachine gun using 9mm rounds. 32 round capacity. Fires rapidly, but its accuracy and killing power decreases as you hold down the trigger, so it's best to fire in short bursts and at close range. Reloads somewhat slowly. One of the four starting weapons in Pro.
AP-1: A submachine gun with a ridiculously high rate of fire. Holds 65 rounds, which it can eat up relatively quick. Has a fairly fast reload time. It's best to fire in short bursts at close range. To unlock in Pro, you must accumulate 50 kills with the PDW-9 in the Basement.
XR-556: A 5.56mm NATO-chambered assault rifle with a 30 round capacity. Its rate of fire isn't as fast as any of the submachine guns, but it makes it more accurate. Has less recoil than the Krinkov, and fires stronger shots. A few shots from this weapon has a 50/50 chance of getting a headshot. Has a reload time of almost 2 seconds. Unlocked in Pro by getting 75 kills in the Hydroponic Garden with the M1370PG.
Krinkov: The AKS-74U from Russia returns from Thing-Thing 4. It fires 5.45mm rounds, semi-automatically or full-auto. Has quite a bit of recoil, so it's best to fire in short bursts. It is unlocked in Pro by getting the Gun Parts in the Cryogenics Lab.
Krinkov Mod-0: A fictitious variant of the Krinkov with a collapsable stock. Has a higher rate of fire and quicker reload times, but the rate of fire weakens the shots, as well as reducing the accuracy. In Pro, It is unlocked by completing all the Cryogenics Lab's objectives in a single round.
M3-556 Minigun: A handheld minigun weapon with an extreme rate of fire. Has a 120 round capacity, and one neat thing about the weapon is that after a short burst, it reloads itself to make up for the rounds that were fired. Firing off all the rounds would only increase the reloading time. Fairly accurate, and useful for crowd control, especially in Zombie Survival mode. To unlock this weapon in Pro, you must get 50 kills in the Service Tunnel with the XR-556.
Hyper Death Blaster: Don't let the name fool you, boys, this is actually one of the two gag weapons in the game, the other being the Murder Snub. It's really an airsoft gun firing plastic pellets that are none too powerful or accurate. While it is the absolute weakest gun in Pro (but its power is uprated a little in Classic), it is one of the fastest-reloading weapons in the games, and has a 200 round capacity. It is unlocked in Pro, along with the SS-500 and Murder Snub, by completing every objective in the Basement in a single round.
Acid Lobber: A weapon capable of launching arcing acidic projectiles at enemies, which then gradually melts them down. While the damage per second isn't too much, the projectiles can splash onto more than one enemy at a time. Has a load capacity of 3 rounds and reloads relatively quick. To unlock the weapon in Pro, you must collect the Gun Parts in the Basement level.
Gauss Pistol: Features a charging system for its ultra high-velocity projectiles. The amount of energy charged into the shot after firing depends on how long you let it charge. One of the most accurate and fastest-reloading weapons in the game. Good for crowd control. Unlocked in Pro by killing 5 enemies in the Blank Canvas level with the Hyper Death Blaster, which isn't easy to do.
Gauss Rifle: The bigger brother of the Gauss Pistol, only it charges energy to the projectiles a little longer, but the shots fired are stronger than the Gauss Pistol. To unlock this weapon in Pro, you must complete every objective in the Service Tunnel.
M35 Launcher: A rocket launcher with a load capacity of 2 rockets. Each rocket is powerful enough to gib an enemy in a single blast. Has a reloading time of approximately two seconds. Useful for getting multi-kills in Zombie and Stinky Bean modes. To unlock this weapon in Pro, you must collect the Gun Parts in the Service Tunnel.
Artifact 23: A high-tech weapon that fires a single, slow-moving orb of destructive energy in a straight path, plowing through enemies without stopping unless it hits a wall, ceiling, or the floor. In spite of its 3 second reload time, Artifact 23 opens up new possibilities for multi-kills, and is surely the ultimate weapon. To unlock this weapon in Pro, you must complete every objective in the Blank Canvas in a single round and/or obtain every Weapon Proficiency achievement in the game.
When you want to build up a high score in the Stinky Bean or Zombie Survival Modes, use weapons that can wipe out multiple targets at a time. (i.e. M35 Launcher, Artifact 23, etc.)
In the Standard Survival Mode where you face armed Thing-Things, and you want to kill them as quickly as possible with the least amount of shots, use weapons like the XR-556, the shotguns, the Model 5-454 and SS-500, basically anything that could kill with little amount of fire.
The Acid Lobber's projectiles may take a bit of time to kill, but when you use a weaker weapon in conjunction with it, the damage from that weapon, combined with the acid can ensure a kill. In short, weaken enemies with the Acid Lobber, and finish them off with another weapon.
Il Duce's name is a reference to the title wielded by the Italian fascist dictator, Benito Mussolini.
The M35 Launcher is the second weapon in the Arena side-series to use rocket-based ammunition, the first being the Gyrojet. It is a similar case with the M3-556 Minigun being a multiple-barreled weapon, along with the Mini-Vulcan from Thing-Thing Arena 2.