At first, I thought the original question was pregame warm-up, as in out beyond the fences before either team has access to the field. There was an Ice team four or five years ago that had a daunting defensive warm-up. Head coach (old age is setting in and I can't pull his name out right now, but some of the other old-timers will post it and I will say "of course, that's it!") could out-Kobata Kobata rolling those two grounders at once and the two receiving players rivaled synchronized swimmers in the way they would charge the ball and throw it back.
Of course when these girls were just taking their warm-up throws in two lines across from each other, they were pretty intimidating. Again, total synchronization and the "pop" of six softballs hitting the receivers' gloves in unison was a pretty good softball version of laying down the gauntlet.
Now, I tried this in unison thing at 12U and ended up with one player sporting a black eye. Don't know whether the head coach or the players' parents will let me try it again, but I'm guessing the players will be extremely focused if we do go back to it.