Pickman's Blade

 is a unique Combat Knife in Fallout 4.

Characteristics
On hit, targets bleed for an additional 25 points of damage.

Locations
The weapon is located inside a wall safe, behind Pickman's painting "Picnic for Stanley". In order to get the key, you must work your way into the lowest room of the gallery, and rescue Pickman from a group of raiders. Afterwards, when talking to him, he will express his gratitude and give you his key.

In order to find the painting he is talking about, return to the front door, then immediately enter the room on the left side of the hall. It will be a picture of a man's face; when the reticle is placed on it, you will receive a prompt to take it off the wall. This will reveal the wall safe, and within lies your prize, along with some caps and a thank-you note.