Each location has a buildable table. I've created 4 things on them so far. Assault Shield, Fan that blows certain doors open that you normally can't access, Turret, and Electrical Charge. The Electrical Charge says "You need to find a source of power" or something along those lines when i place it down and now this new electrical zombie thing seems like it can be a solution. The final location has a buildable table, but no items round to find. I found one halfway through a bus ride. I jumped off and found it. Now, I've also noticed another spot where I can jump off the bus and search for another part, but I died before I could. Theres also a thing on the roof of a place that says parts required, but everything I've tried so far says "Wrong Part." Theres one door on the map that looks easter egg related (just like the door from Call of The Dead and the character says something about it when you push X. I still haven't found the pack a punch or the wonder weapon; however, I believe these parts I'm finding right now create the wonderweapon or a motorcycle, cause i saw a cycle in the trailer and theres an achievement for using an alternate form of transportation.