Here's a fun one.
My very first concert was Styx, The Grand Illusion. I was in 9th grade. They were not yet the huge arena-filling band that they would become, so the gig was at the local ice skating rink that sometimes had "events" with the ice turned off and turned into Main Floor seating, but we had seats in the stands.
The opening band was Ram Jam, the one-hit wonder known for "Black Betty". They were actually really good. Opened with "Black Betty" of course, then played a bunch of other songs that no one knew but were pretty good rock and roll. I remember a couple more of those clever, syncopated breakdowns and stuff not unlike "Black Betty", and even though no one knew any of them, they kicked some ass. They even got an encore, but they'd played all their songs (their 34-minute self-titled album would be an EP by today's standards) so they just played "Black Betty" again. Bam-ba-lam. Then Styx came out and blew them away anyway.
If I could go back in a time machine and see them again, I'd probably be disappointed that I'd even bothered, but at the time, it was awesome! My first concert, so the opening band, Ram Jam, was the first "real" band I'd ever seen, and they rocked the house. Rock and Roll!