A few balance suggestions:
Mion Cannon feels underpowered, as it's slow and doesn't deal much damage. Maybe increase the duration of the laser or increase its damage a bit?
Yubivolver feels a bit too powerful. Maybe make it so you have to click for each shot?
Handmine can be strong in the right situations, but maybe decrease the recharge time a bit so more of them can be placed?
It doesn't really make sense why the range of the chainsaw would decrease while you're moving forward and increase while moving backwards. I think it should be constant in all directions regardless of movement.