I'm old (by today's developer standards) and have seen a lot of things come and go, pushed by the corporations, hyped by the media and worshiped by the masses :-)
Basically, I'm not easily impressed and couldn't care less for the next super-duper js library or another reinvention of the wheel. But from time to time something really breathtaking comes along. Here are three things that to this day I still consider mind-blowing.
To this day I think there was no bigger single leap in consumer hardware performance than this. It felt like a personal Silicon Graphics workstation on a graphics card.
Back in the day, this was like something straight out of the future. Tiny mechanical hard drive with spindle motor, head servo, controller, power electronics etc., all packed into Compact Flash enclosure. I think the miniaturization level is still very impressive today.
I feel really sorry that Wave failed so badly. None of the components were really groundbreaking or even that new, but they just fit together in a good way. It was the classic case of the whole being more than the sum of the parts.
Probably the most influential programming language/paradigm/philosophy ever. Need I say more.