⌘⇧X is an addition to cut, copy and paste: swap. It copies and pastes at the same time.
It's useful, for instance, when pasting selections into each others' positions--that is, swapping two blocks of text. You cut one, swap the other and paste it back.
I've been editing text--copy and code--more or less all of the time since forever. I edit visually, pasting existing text around as much as possible. (I just ⌘⇧Xed “copy” and “code” up there to follow my career chronology.) Once a day or so, I find that I have something in the clipboard and something selected, and need to swap them. So here we are.
⌘⇧X is now set.
$ defaults write com.[vendor].[App] NSUserKeyEquivalents -dict-add "Exact Menu Command..." nil
Happy Swapping,
Nicholas Hall
© 2013 Nicholas Hall. Whatever tho.