Cute graphics and I like that each gun has a different shot pattern. I also like that you added an arrow indicator for the exit, it's helpful especially for the big maps.
I would remap the E/F keys to the spacebar. Since movement is with WASD, it feels awkward to let go of the index finger and temporarily stop moving when I'm trying to pick up or drop a gun. I'd also remap it to a single key and just have it detect if you have a gun or not.