Not exactly jaw-dropping, but I thought they were pretty amazing the first time I experienced them: Virtual Machines (precisely, VMWare). SSDs LCD monitor Amiga 1200 (seeing some amazing demo on it really was mind-blowing) Action Replay (C64 cartridge which allows you to dump the whole machine's RAM to disk and later reload it, essentially giving you machine's snapshots, e.g. save games for games which didn't have th…
My dad had a friend with an MSDN subscription, so we got a pre-release developer copy of Windows 95. Moving from Windows 3.11 to that was pretty jaw dropping.
But after a while we had an issue with the machine. Sectors on the hard drive were going bad, so we brought it into a shop to have someone confirm that. When we booted it up in the shop the tech's eyes went wide and I think he started drooling a little bit. He offered to swap the drives and copy all of our data from one to the other for free (I assume he thought he could make a copy of the OS for himself too). We declined and he was pretty crushed.