These tiny microscope cards allow you to magnify samples from 500 to 1,000 times depending on the amount of ambient light and (my favorite thing) how closely you view the lens. They're disposable, too—or rather designed for single use—and are not cheap at $90 for five.
Suggested uses: checking blood counts; checking hair for dryness; making sperm counts.*
* Von sperms. Ah ah ah! Two sperms. Ah ah ah!