Just a few off the top of my head
The Amiga: Simply mind blowing at the time, so many colors, multitasking and so on, what a giant leap from the C=64 I had.
TurboGrafx 16: Coming from the NES, and seeing the HUGE sprites in China Warrior(shit game but great tech demo)
Laserdisc: The jump from VHS and pre DVD was amazing, and seeing it on a nice set through s-video was something to behold.
And one thing that didn't amaze me that much
The Internet: This did little for me as I had been doing the BBS thing since the C=64 days on a good ole 300baud modem.