It is still the wheel. Almost all mechanical things have wheels of some types in their designs. It is not necessarily the wheel itself but the concept of round items that "roll". Gears are modified wheels. So many things are derived from the wheel. Find any item that is mechanical in nature and then see if it uses a wheel or the concept in it's design. Most things will. Certain items like transistors may be incredible pieces of technology but could they have been designed or manufactured without a wheel in some way.....if they could be could they be delivered to the end user without a wheel being used? Wheels are EVERYWHERE and in EVERYTHING. This is merely my opinion of course so I could be wrong.
But if it had to me something more tangible: sanitation. Without sanitation, none of the responses from those above me would matter. You aren't getting the internet or microchips without clean rooms. You aren't going to get good medical care without sanitation. And mugs, without sanitation, would you really want that sex?
The fax machine. It really changed the way business is done. The fact that documents could be sent to locations all around the globe in a matter of minutes were the first step of the information revolution.
I absolutely agree. Humans existed for more than 100,000 years in a hunter/gatherer society, and everything you see today in relation to technology would not have happened without agriculture. Agriculture allowed humans to congregate in one place and develop the social and economic foundations of what we have today. No question - agriculture ftw.