Find the following hidden boxes: the first is located in Freigh's head (the robot over the church), the second is in the staff room under pack a punch (follow the wooden planks), and the final one is in Agartha near the fire staff portal.
For this trophy you must create the turbine, which is composed of the parts in the bus stop at the start (one against the sign in the middle, one beside the bookcase next to the M14, and one on the bench next to the power needed door). Just place the generator at each door of this sort at each stop (bus stop, diner, farm, city, power room). One will not have a part; the other four will. Place the ladder on the back driver-side of the bus, the grill on the front, the emergency ladder on the emergency exit on the inside. If you wait until a zombie destroys the ceiling, you can skip the fourth part. If not, there is a fourth part to attach on the emergency exit.
You can kill the giant a number of ways but he can be resistant to some guns. Effective guns include the Acid gat, Death machine, Lsat (with headshots), or a LMG with the Deadshot Daiquiri perk doing headshots. These will usually kill him without wasting too much ammo.
Note: You must be playing in tranzit. Revive the same teammate 15 times or more in the same round. A green flash will thenpop out of your teammate, meaning you unlocked it. It is recommended to try this in round 1. Now you can revive your teammates quicker without buying the quick revive perk. This unlock will be saved in your profile troughout your future tranzit games.
To hear the hidden song, find and activate the following hidden green rocks. Note: There is no prompt to interact with the rock. The first rock is located in the spawn room at the corner near the Generator Room 3 door. To find the second rock, leave the starting area and go toward Generator Room 2. Follow the route to the workshop through the trenches and locate the sign that points to No Man's Land. Unlock the bunker door, go upstairs, and search under the bunk beds that are against the wall. To find the final rock, open the door to No Man's Land and follow the signs to the Excavation Site. The rock is hidden near some crates that are in a corner of the map to the left of the Excavation Site.
Get a collateral head shot with one bullet to permanently unlock Deadshot Daquiri, a perk that increases the head shot multiplier in zombies and is saved to your profile. To confirm you have this, shoot a zombie anywhere but the head until it dies. If the head is magically blown off, you indeed have the perk.
Is it true that A7X is featured in this game?
I heard that it was but i'm not sure.
Answer from MrClancy
After the campaign is over there's a scene with Woods and Menendez in 2025 playing with A7X doing the song "Carry On" with a bunch of characters dancing. It's pretty comical. You can actually watch it on YouTube as it doesn't spoil the story in any way.