I've always found the multikill pitch change in this game to be really satifying to hear. A skin bundle where this is played into more would be amazing.

There could be a music themed skinwhere ALL the guns sounds change to match the multkill pitch change. Each gun or skin colour variant could be themed on a different instrument or play a different tune. A fast ace could play a nice beat into a solo when you get the final kill. Maybe this could be a collaboration with another artist, or Zedd 2.0?

You could have a skin that transforms or powers up with higher multkills. You would only be able to see the final form with an ace, maybe even a hidden one for a 6k.