Magnets. Magnets belong in the Shire. Who can fail to be entertained by them? You can take them and click them together to make fun noises. You can set one on a desk and one under it and make them zoom around playfully. You can clean up paperclips and nails and sort metal from paper in seconds with almost no effort. But the best part is sitting and trying to force together the opposing sides of two really powerful magnets. It... just... won't.... work.........
And I send my best friend at school for knowing me well enough that instead of candy or something "typical" of souveniers, she brought me magnetic rocks and glow-in-the-dark nail polish.