1) Steel wool: how many times have you ever been scrubbing and scrubbing at a dish because the caked junk at the bottom wouldn't come off. Well, here's your solution. Sure, it can get rusty, and after a while it starts to stink, but steel wool can be a big timesaver in the kitchen.
2) Google: simple, easy to use, and dead useful for research or just finding out about the one thing that you are interested in. Google has saved me from failing projects on numorous occasions. I also just google random things that I'm curious about. If you want to enjoy google, I suggest that you don't think about how google is tracking everything that you search and putting ads that they think will aplay to you based on that.
3) The wheel: An obvious one, but worth mentioning. without it, life would be very different. Imagine hula-hooping with a square hoola-hoop!
4) Cars: Just don't think about the insane amount of greenhouse gasses being released and the wildlife you are killing when you drive, and you have and easy, fast means of transportation to get you where you need to go. Same goes for airplanes, but on a larger scale. Kills more wildlife, but takes you more places.
5) Underwear: Just think about not wearing it. Just think about it.