I just started using a controller to play Spiral Knights. Sure, it's not the most precise thing, but it's really fun for me. Using swords and bombs are fun and easy, but guns and vials are really hard to aim. When using a controller, the arrow that replaces your mouse cursor disappears altogether. There's no precise visual cue to tell where you're aiming.
I'm here to suggest that some sort of laser or line show us where we're aiming, similar to what they have on Dead Nation or Alien Swarm. If laser doesn't fit the art style, maybe a cartoon-y dashed line would fit better. The line itself may be semi-transparent. Maybe it can only show up when a gun is equipped or a vial is being used. Maybe it can only show up when that arrow disappears. Maybe it should be toggle-able!
It could also be used to determine a gun's range. (Just throwing that out there)
Would be pretty handy, definitely. I don't like it when my bullets show the hit animation and then I realize that there's no damage being done just because I actually was a few pixels off and didn't realize it. :s