Only one other creature on the board before playing Skeleton.
I'm curious. How would you "use" a 1-atk creature while your opponent has a 1-shield in place? You're obviously not using the Skeleton to deal damage, so what benefit does it give you?
It depends on the deck. Did he have

quanta? (Bonds) Did he have

or

quanta? (bye-bye shield) Did he have

quanta? (Pandas or Chaos can make a RT) Did he have

quanta? (Momentum, though it would be a stretch, maybe even Catapult) Did he have

quanta? (Dry Spell usage) Did he have Luciferins to fuel Hope? Did he have

quanta? (Bonebolt if you are desperate)?
If none of these apply, then you have absolutely no benefit. If you do have one of these, then why not. Also, if I know I don't have enough creatures to fill the board, I would pull out a Skeleton just for fun.