Once I got to SFMM at opening and I rushed straight to Terminator: Salvation. It had only opened about a month earlier, so I was surprised to find an empty station when I got up the stairs. I managed two solo rides in a row in the front seat before other guests began to show up. Definitely something I'll never forget.
At Knott's, the only notable instance was getting my own boat on Perilous Plunge. I still got totally soaked.
At USH, I've managed my own car on The Mummy, my own boat on Jurassic Park, and on my first trip ever through Transformers, I had my own EVAC all to myself. I tell you there's no better way to first experience a brand new blockbuster attraction than with your own private viewing!
There's been plenty of solo trips at Disneyland including Space, Splash, Indy, and Pirates. But the best one was when when a friend and I rode TOT on a rainy day and got our very own elevator to ourselves!