1-) Secret “Dom’s Tom” tomato grenades
Play Act 2 – Chapter 2: Geared Up on any difficulty. Progress through the chapter until you takeout the helicopter and proceed forward to the greenhouse. After killing all the enemies that appear when you enter the greenhouse, destroy the approximate 10-15 tomato plants found inside the greenhouse, including one kind of hidden on top of a shelf. Once you have destroyed them all, Marcus will begin ranting (with lots of cursing) for around a minute about all his tomato plants being destroyed. A new tomato plant will then appear on a table at the exit to the greenhouse. Interact with it to get six tomato grenades called Dom’s Tom that can be used like normal grenades, except they explode with lots of red tomato sauce.
2-) Giant Leviathan Easter Egg
In the Harbor multiplayer map, shoot the six little Leviathan statues around the map in a specific order, then activate the switch at the Longshot spawn to get a giant Leviathan to jump out of the water.
3-) Secret “Despicable You” weapon
Start a new game on the Insane difficulty. Proceed through the beginning of the Prologue and destroy the Comms Tower and then grenade the bunker in order to make it to the large gate. It is recommended to grab a new set of grenades at this point to make killing the three enemies you will encounter next a little easier. After opening the door, go to the main gate and interact with the panel on the side to start a short cutscene. Continue to the next section, which is where you can get the hidden weapon. When you come out of the gate, kill the three enemies you encounter. Then, sprint forward towards the stairs, and turn right before the stairs to see a gate starting to close. You need to dive through the gate before it closes. If you fail to make it through, simply reload the last checkpoint and try again. The gate closing seems to be triggered by the final enemy dying. Once you make it inside the room before the gate closes, you will find the “Despicable You” weapon on a container on the left. This weapon is an ice gun with 12 bullets that shoots an ice ball that freezes and kills any enemies within its radius. Unfortunately, this weapon can only be found in this location and the ammo for it can not be replenished. This weapon is a reference to the Ice Gun in the Despicable Me movie.