Big Jim is a one of the unique weapons, a unique wrench in Fallout 4 that has a special ability to cripple the target’s leg with each hit. Big Jim can be found at the Walden Pond, a location southwest of Sanctuary Hills and northwest of Cambridge Police Station.
Open your Pip-Boy and fast travel to the closest location to Walden Pond if you have already discovered it. If you haven’t discovered it yet, head southwest from Sanctuary Hills or northwest from Cambridge Police Station.
Once you arrive at Walden Pond, you will see a small gift shop near the pond. Enter the gift shop and head towards the back room. In the back room, you will find a trapdoor that leads to an underground area.
Note: The underground area is full of low-level enemies. Nothing to worry about but come prepared with ammo.
Open the trapdoor and descend into the tunnels. The tunnels can be a bit tricky but follow the path until you reach a room with various machinery and tools. Look for a metal shelf; Big Jim will be lying on it.
Alternately, you can use the Drainage Pipe in the Pond itself to access the underground area that leads to Big Jim’s location.
Once you locate Big Jim on the metal shelf, simply pick it up, and it will be added to your inventory.
