The music was amazing and I generally liked how the game felt and looked.
Pickups desperately need to play some sound effects (unique to each pickup).
The player needs to play some kind of sound or have better indication that they're taking damage. There were plenty of occasions where I was dying and had no idea it was even happening.
Perhaps some kind of indication as to where I'm taking damage from? I realise old FPS didn't do this, but...
Some kind of low-health indicator might be useful, even if its just the modern red aura along the sides of the screen or something.
The katana felt kinda useless to me, a little too useless! The Pistol felt great! The Railgun I didn't really get enough time to try as I ran out of patience by the time I got it.
Combat needs better feedback, generally. When swinging my hanzo steel at someone I had no sense I was actually hitting them or not. Some enemy grunts and slicing sounds + blood/sparks should be enough for that.
Enemy variety is a bit too thin.
Aside that, I like the cutscenes and the writing was entertainingly silly. There's also quite a lot of content given the time-frame of the jam! Good job overall, just needs a few things here and there to really bring it together imo.