Weaponsmith

 is a Fallout 3 achievement on Xbox 360 and PC and a trophy on PlayStation 3.

It is granted for constructing one of each custom weapon. Those are:
 * Bottlecap Mine
 * Dart Gun
 * Deathclaw Gauntlet
 * Nuka Grenade
 * Railway Rifle
 * Rock-It Launcher
 * Shishkebab

Strategies
Probably the easiest way to obtain all of the parts necessary to build all of the custom weapons is to go to Lucky's south of Tenpenny Tower. This location contains nearly all of the parts needed to make every single custom weapons. No Deathclaw Hand..sorry.

Bugs
Sometimes after you have made each weapon, the game doesn't give you the achievement/trophy. However, this may be due to finding one of these weapons rather than actually constructing it. This was confirmed for me when I constructed the Bottlecap Mine even though I already had two of them that I had found; and the achievement was awarded.