Fallout 4 Scrapper Perk: Scrapping Weapons Example (Rank 1)
A short video of what materials a bunch of random wasteland weapons provide with the Scrapper perk rank 1.
Scrapped weapons:
Laser Rifle (0:14)
Short Hunting Rifle (0:17)
Fat Man (0:20)
Pipe Pistol (0:24)
Short Pipe Bolt-Action Rifle (0:26)
Short Double-Barrel Shotgun (0:30)
Short Combat Rifle (0:32)
Submachine Gun (0:35)
Security Baton (0:40)
Switchblade (0:43)
Pipe Wrench (0:45)
Ported Heavy Combat Rifle (0:48)
As a conclusion it is quite obvious that the perk is very useful for finding some of the uncommon salvage in the wasteland (e.g. aluminum, copper, screws). The heavier and more expensive weapons usually give out better parts. Also it is evident that the more mods a weapon has, the more and more valuable scrap it provides. As seen from the video, unmodded melee weapons only provide steel which makes collecting them for scrap useless. Same goes for pipe pistols. Heavily modded pipe pistols, however, should be one of the best weapon types to collect for scrap as they a) don't weigh much b) have very low value (useless to sell) and c) should contain a fair amount of valuable materials