Never seen it,
EDIT:
Ok one problem with your reasoning. The reason for instakill spam is the armor and always will be. Those op weapons came after the armor update as well as the buffed weapons.
@RiliSoft Pixel gun sucks for anyone who knows how to play, now new players can easily take larger amounts of damage off veteran players without trouble. This is because of armor and over powered weapon selection, not to mention how difficult it is being new and without fully upgraded armor on...
Hold up, all the guns were nerfed when they gave them extra damage for armor, it wasn't always like that. So they should make those changes for a no armor mode, I would be so happy. Anyways it wouldn't be a big deal if they made it like v7.1 for the no armor mode when there were no op guns...