Interesting, I happen to like it. The variety of weapons is pretty nice and some of the weapons are actually really cool, I think letting players Have two weapons That they can toggle between or requiring that items are picked up with a button press would probably be more beneficial. It can be somewhat irritating when you have a weapon you want to continue using and lose it because a pick-up spawned on top of you or any various other ways an unwanted gun could be picked up.
I feel as if the inability to aim up or down while firing, coupled with some of the ways that maps are designed actually hurt this game quite a bit. It was far too often that I found myself in situations where fast-moving bots were clustered into small areas that are difficult to reach, or when falling through the bottom and I died because something moved into my blindspot where I was unable to shoot it. I feel this makes for a lot of uneeded deaths for the player which could make the game more frustrating.
As for the stage designs, I felt like a lot of the designs were somewhat clausterphobic and the way the barriers are placed generally benefit the bots more than the player. Also, because there are often so many barriers, certain weapons are quite a bit weaker than you probably wanted them to be. Like the viral gas, I have to move to the right position to use it, but if bots are just boxed apart from each other, it loses much functionality because it will only kill one or maybe two bots at a time. The stickybomb functioned much better in most cases as a delayed kill weapon thanks to the fact that it can actually travel straight down and land on stuff through the screen loop. So I can kill stuff without having to often leave safe positions.
I also often found myself sticking to the laser and hacker because they offer such large payoffs compared to other weapons, with the hacker, you can clean out a stage pretty fast, especially if you get one of those gun-toting commandos. and the laser's ability to shoot through walls speaks for itself. I'm not sure if you were looking to encourage the player to prefer certain weapons or wanted them to play with a variety so I was just pointing that out.
Now this next part is just an idea I got but here's a possible control setting for two players.
P1 keeps wasd but instead they can choose to fire with C or Ctrl and player two could get the arrow keys or the numpad and can still shoot with enter. The idea here being that both players get as much room between them as needed and only need a single hand to play the game without having to take fingers off the movement keys at all. I don't have any problems with your current controls or anything it just seems like a nice idea.
Anyway, nice work.