Deafening Silence is one of the best answers to Omni-Tell, limiting them to a single noncreature spell per turn and severely hampering their ability to chain Ponder, Brainstorm, Stock Up, and then Show and Tell into Omniscience or Atraxa, Grand Unifier in the same turn. Pyroblast can counter Show and Tell, Force of Will, or any other blue spell, or destroy a resolved Omniscience before they start chaining free spells. Static Prison is far too slow against a deck that can win the turn Show and Tell resolves, and Goblin Bombardment/Sand Scout don't interact with their combo plan at all. Apply early pressure and hold up Pyroblast for their key turn, since this matchup is decided by disrupting the combo before it goes off.