My list is my own. Each item on here has probably been individually included in other "best 10 ___" lists out there, but this group of items, along with their descriptions, is my own. I've also taken liberty to cut down the list to 5 entries... makes it more readable and appreciable.
Utterly sustainable. Runs on renewable energy with no pollutant emissions... makes user healthier while performing an energy efficient service. Very affordable.
2. Anti-biotics & bottled vitamins:
Although two seperate items (both invented in the 20th century), I group them as one, because together they helped eliminate a MASSIVE proportion of illnesses. Illnesses which were once considered fatal (or even "plague") are now easily dismissable and threatless.
3. Integrated Circuits:
These are a little discussed (seemingly common) component of any modern computer, but their implication is huge. Any "self-intelligent" piece of equipment (from your car to your cell to your washing machine) contains an integrated circuit. These have made communication as we know it a universally accessible thing, by way (initially) of mass media, followed by computers, eventually followed by the internet itself. All of which lie requisite to a small circuit upon which lies your microprocessor, silicon wafers, capacitors, and many other items which people smarter than I have assembled.
4. Public Libraries:
For as little as $20 a year (cost to individual taxpayers), everyone is entitled to a library card, which has the potential to grant them access to untappable amounts of free knowledge and entertainment. A library is one of the world's breeding grounds for shared ideas and expansion of human knowledge. Not to mention a selection of books with entertainment value that you could not fully extract in a lifetime of reading!
5. The Sari:
As far as personal clothing goes, this is the most adaptable and useful piece in existence. It is made of a simple strip (uncut & unsown) of fabric straight from the loom which can be made into a modest (or imodest) outfit of varying styles, can be adapted to include a sling for a baby or firewood, can offer covering for one's head when shade (or modesty) is required and can be adapted for comfortable walking, running, bike riding, wading, and most any activity in the day-to-day human experience.