In MW3 Zombies, the Ray Gun is a Wonder Weapon you can use to slaughter enemies fast. I've had to play around 20 matches before I found a Ray Gun, so here are some methods you can try in-game to get this weapon quickly.
How to craft a Ray Gun in MW3 Zombies
After obtaining a Schematic for the Ray Gun, you can craft it through the Schematic Crafting section in the Gear tab. Keep in mind the Ray Gun is a legendary Wonder Weapon, so it has a 48-hour cooldown.
Obtaining the Schematic can be tricky, and your best bet is to complete as many missions as possible in the high-threat zone (red). Eliminate Mega Abominations, complete Deliver Cargo, and participate in other missions in this zone to get Schematics for Wonder Weapons.
How to use the Ray Gun in MW3 Zombies
The Ray Gun is a Wonder Weapon and you can obtain its Acquisition (one-time use item) or its Schematic (craftable item blueprint) during a match in MW3 Zombies. Obtaining an Acquisition for this gun is rather easy compared to getting a craftable Schematic for it. The Ray Gun has a 20-shot magazine that can easily devastate powerful enemies in the higher threat zones. The best way to obtain this gun is to complete different types of contracts and defeat special zombies around the map.
The drops from Reward Rifts are given at random, so you'll have to keep completing contracts and missions to obtain legendary Wonder Weapons. I obtained this gun after completing an Aether Extraction contract in the medium-threat zone (yellow). You can target other contracts in the higher threat zones to obtain the best items from the Reward Rift. For example, try easy contracts like High-Value Target, Deliver Cargo, and Raid Weapon Stash.
How to level up the Ray Gun in MW3 Zombies
You can level up the Ray Gun by visiting any of the Pack-A-Punch machines around the map in MW3 Zombies and spending Essence to upgrade the weapon. Remember, Essence is the primary currency used for Pack-A-Punch upgrades, so complete as many contracts as required to get the necessary credits. I recommend completing bounty contracts as these require eliminating special zombies like Mimics, Disciples, Manglers, and Mega Abominations.
Pack-A-Punch upgrades cost up to 15,000 Essence, so you'll need to collect a lot of it. Alternatively, finding or crafting Rare, Refined, and Flawless Aetherium Crystals allows you to instantly Pack-A-Punch upgrade weapons to a higher level. These crystals save you the trouble of finding them through regular looting for weapon upgrades. Either way, if you are looking to get your hands on these upgrade tools, visit Infested Strongholds, Aether Nests, and Mercenary Camps around the map.
For more quality guides and useful information relating to Modern Warfare 3, check out Where to get a Dead Wire Turret Circuit in MW3 Zombies right here on Pro Game Guides.