Not just for the science-types, these test tube favors are really, really cute (not to mention, super easy to make):
You can get them in various sizes, fill them with your favorite candy, slap on some custom labels (any kind of sticker, really), and you're done!
But why stop there? Maybe you like bath crystals, flower seeds, even little spice or tree seedlings. You could even stuff them with hand made bracelets, a ribbon necklace, or anything else you want to give with love!