Bubble wrap, the classic. The original. The one that started it all. A roll of 12, each individually wrapped in its own little plastic pouch, just begging to be unwrapped and re-wrapped in an endless cycle of joy and frustration.
It's the perfect combination of tactile, auditory, and visual stimulation. A symphony of bubbles popping, each one a little surprise, a little thrill, a little 'oh no, not another one!'
You can find more varieties of bubble wrap at Extra Bubble Wrap or Surplus Bubble Wrap.