Few things, not sure if people are aware of or not.
-
If you play as Nikolai and get 4 molotov and throw one at the ground under the lamppost next to the ammo box in the sort of alley with the wisp tea machine then fiery footsteps appear and stop if you throw another where they end then more footsteps appear. Repeat this step until you reach a small cave entrance and throw one at the floor of that entrance then hold the interact button (X or square on controller) then it will trigger a cutscene where Nikolai goes into the cave and you see his past and get chased by a demon and ravagers until you exit again, when you exit you are rewarded with a legendary weapon and some other stuff.
-
If you have the LGM-1 wonder weapon from O.S.C.A.R. this is not classed as a WW in the map it is an Artefact so you can also hold a 2nd WW with this gun. (I had Mule Kick active when I done this, not sure if that is a necessary step to own 2 WW)