Second reality was the first demo I every viewed; quite by accident, too; I thought it was a differnt program then what it was. It took me 2 1/2 hours to download on my 2400 back in the day.
I ran it.
I watched it
I was enlightened.
...and completely blown away.
It was, and still is, the most amazing piece of coding I have every seen. Amazing morphing, great music and even Dolby Digital sound (where available). After that, I aspired to be a demo programmer.. and I would have become one, too, except that I sucked.
Yeah, sure, they had others, like the venerable Fishtro, Mental Surgery, Unreal and Soupa, but Second Reality has the number one place in my heart.