Here is a list of the location of all the weapons along with all their ammo schematics.
Plasma Cutter - found shortly after your first heart pounding run in chapter 1.
Plasma Energy - Preloaded in Store
Line Gun - Preloaded in Store
Line Rack - Chapter 2, behind the door that requires a Power Node.
Pulse Rifle - Preloaded in Store
Pulse Rounds - Chapter 2, in a room with a man choking on his own vomit. Should be around one of the first times you actually use your Grip ability.
Flamethrower - Immediately at the start of Chapter 2, right after you pick up the kinesis module.
Flamethrower ammo - Chapter 3, through a door next to the first store you come across in this chapter. It is on a shelf close to an Audio Log
Ripper - Chapter 3, close to where you use your grip to restore fuel. It should be right in front of the grip thing.
Ripper Blades - Chapter 3, behind the door that requires a Power Node
Force Gun - Chapter 4, when you get off of the elevator on the third floor, it should be in front of you.
Force Gun ammo - Chapter 5, in the same room that you meet the annoying mutant that doesn't die. Its called a regenerator. (I think.)
Contact Beam - Chapter 4, when you get off of the elevator on the first floor, it should be in front of you.
Contact Energy - Chapter 5, at the start of the chapter, close to one of your only friendlys in the game.
Edit: As for all of the med pack schems, those should be on the ground throughout the mission. They are really hard to miss.
Another thing is that once you play through the game once and get all of the schematics, you do NOT have to get them all again. You can completely ignore schematics in your second play through, and that should save you a ton of space in your inventory between missions