The humble ball point pen. People forget how cumbersome and/or expensive it was to write before cheap ball point pens became a thing. You had to use fountain pens. The cheap ones leaked and were an absolute mess to carry around. The ones that didn't leak were expensive. I can now buy more pens for $100 than I'll ever use in years and just stash them everywhere I want
Haven't pencils always been inexpensive?
Then you have to carry around a sharpener with you everywhere
Never seen anyone walking around with a pencil clipped to their shirt pocket.
How do you learn writing? In Germany, as far as I know, everyone learns writing with foundation pens. You can search for images with „Schreiblernfüller“ to get an idea how they look.
In the US ive never used or even seen anyone use a fountain pen, although ive heard of enthusiasts for them here.
I predominantly write with a ballpoint pen, however as an affection when I write letters (which is more often than you might think) I always use quality stationary and a fountain pen. I'm very American. I know it's not commonplace, but in many ways that's exactly why I do it. There's several rather successful businesses in the US that only supply fountain pen users and collectors, probably the most well known is the Goulet Pen Company https://www.gouletpens.com/
Hand washing. Modern disease control and prevention is borderline magic. Hand-washing is clearly the most important lifesaving and disease preventing invention in modern times. Materially ... Well, "yourself" precludes anything computerized, unless you mean "program". It also precludes a huge range of materials science advances. Technically, you can make steel and concrete yourself with enough real-world minecrafting…
I wouldn’t call it a recent invention although it might be recent in the west, but plenty of cultures in South Asia, Iran, and muslim world (at the very least) considered hand washing crucial for basic hygiene.
At the risk of being controversial, perhaps the most modern simple invention is the internet and its ability to let randoms ask a basic question and have a thousand people contribute hundreds of cumulative man-hours to answering it.
(Maybe I'm being cynical, but I feel like the OP is asking this question for reasons beyond pure curiosity.)
Pads and tampons. Some argue these are environmentally unfriendly and produce too much waste, but you have to think, not everyone is privileged enough to own a washing machine in their own home, particularly those in 2nd and 3rd world countries. I genuinely believed pads and tampons allowed women to be more productive in the work force and eventually lead to more equality, just hearing my mom and grandma's story of h…
I live in New York and the majority of my friends do not have washing machine in their home. In fact, it’s a luxury to have one. In contrast, I’m originally from Ukraine where not having a washing machine is weird to say the least. There are many things that would make me call US a 2nd world country, so I’m having a hard time understanding which countries are 1st world countries.
After WWII, there were two superpowers splitting the world between them: the first world was the NATO West, and the second world was the Soviet East. Countries who were unaligned, or not considered sufficiently important, made up the so-called third world. If these terms ever meant anything, they don't anymore, and they certainly have nothing (directly) to do with washing machines!
Someone didn’t think of putting wheels on luggage until relatively recently, in 1987. https://www.nytimes.com/2010/10/05/business/05road.html
It needed development of tough plastics to become practical. Until very recently you had to be careful to get bags where the wheels wouldn't snap off eagerly.