I haven't heard anyone mention the PowerBook G4 yet but that product casts a long shadow. I remember the impact when they released it, there hadn't been a laptop like that on the market. And they haven't really deviated from that esthetic for their laptops since then.
2012 15-inch retina macbook pro. I used it for 5 years and even then could have happily stretched it longer. It lasted me well into the era of terrible macbooks plagued with problems. The performance even held up, with its discrete GPU and formidable processor handling pretty much everything I threw at it. In lots of ways it was superior to even my current 2019 16" like port selection (display port, HDMI, SD card, USB-A), real f-keys instead of useless and annoying touchbar, smaller and less accidental-input-prone trackpad, magsafe, headphone jack on the left side (the only side that makes sense), and better user-serviceability. It so far outclassed every other laptop at the time that you can't really even compare. The things I built with that computer and learned while using it transformed my career and my life.
Macintosh 512K aka 'fat' Mac. Increased memory made it suitable for business use. Built-in Localtalk file sharing, plus the Laserwriter came out around the same time.
I enjoy most Apple products, but AirPods were the first product I truly felt were magical. (I also think being a game changer doesn't necessarily correlate with being the best designed product of all-time... just a product that was better than the competition at its inception.)
The iPhone, because it gave way to the app store, freeing us from all the previous crappy phone experiences. Think about how many industries and new products were created from that product. Amazing.
I think it depends on how old you are...for those of us who remember a time before personal computers, that first desktop was mind blowing, but the social game changer was going from a huge tower or 50 pound book of CDs to carrying all of your favorite music in your pocket at just 5-6 ounces...for the iGeneration, airpods.