The Shrink Gun is the same as the one in Shangri-La, when you hit a line of zombies, they'll all turn into a baby that you can shoot like a soccer ball by running into them.
You can either obtain it in the mystery box or by crafting it, and only one player can possess it at a time.
The first step to get the Freeze Gun and the Gravity Gun is the same : you have to build the kit and place a Shrink Gun frame on it.
To build the kit, you'll have to gather 3 pieces that only have 1 location each. The crafting bench is in Broken Arrow Factory.
At the entrance of Broken Arrow Factory
To the left of Elemental Pop
At the ground floor of Farm House
Then you have to find a dynamite that can spawn on one of the pole around the map, shoot and collect it :
Then place the dynamite on the box between the power and the pack-a-punch statue at Broken Arrow Factory, take the frame and place it on the kit.
The Freeze Gun is really similar to the Baby Gun, hit a line of zombies they will all freeze, and then you can run into them to break the frozen zombies.
The big difference is that if you shoot a second time, on a line of frozen zombies, they will actually die (and really cool ice effect).
In order to get the Freeze Gun, you'll first need to get the keycard by interacting with the drawer at the first floor of the Farm House, and then interact with it again to get the keycard. After that, you'll be able to grab the Ice Relic at Broken Arrow Factory and dive it into the cooking pot on the table at 32 Yungaro Way.
The final step is just to hold the Ice Relic in the stand next to Deadshot Daiquiri at Church. When it's done, come back to the Broken Arrow Factory crafting bench, add the Ice Relic to the frame and congratulation you got the Freeze Gun.
The Gravity Gun is a powerful wonder weapon if used right. Hit a line of zombie, and they'll start to float before exploding.
It might seem a lot better than the Freeze Gun, but it's harder to get and the Gravity Gun range is smaller.
The first step to get the Gravity Gun is to get Thunder Wall on one of your weapon and get a kill in front of the pot in 32 Yungaro Way to be able to grab the Gravity Relic. After that, you will need to run through 11 purple orbs around the map and congratulation, you can put the Gravity Relic on the Shrink Gun frame and grab your Gravity Gun.
The Puke Gun is the main wonder weapon of the map. When you hit a zombie, he will get sick and start running into other zombies to puke on them.
It's the most powerful wonder weapon on this map, but it's also the less useful since you can't get away from being cornered, and won't kill zombies quick enough to revive your downed mate.
The Puke Gun is only obtainable through the magic box and have a crazy low drop rate. The only way to make the drop rate higher is by doing the Main Quest : one of the steps requires you to have it, so the rate goes significantly higher.