Usually in weapons crates. Purple and orange weapons are the rarest. You find rarer items in the second playthrough.
Random.
You cant make weapons in borderlands, you find them, (i finished game)
rider and something else
Crawmerax cannot drop gearbox weapons
You keep all your weapons and skill levels when you start the second play through.
you have to find them orget them from qeusts (i get alot from red weapon cases)
go to the gun shop at the bottom there should be gun mods. i think
Blue, Yellow, Cyan, Orange.
They r in all of the gun cases, It will just b a luck of the draw to get them....
sorry that's not possible because the game uses a random gun generator so u could get an orange atlas with damage of 2 or u could get one with a damage 0f 800so good luck!
There are vending machines at certain places where you can sell any unwanted loot and buy new weapons.