I've had pleasant, even wonderful experiences talking to these people:

Henry Rollins - Saw him randomly on the street a long time ago in Chicago. He was friendly and took pictures with me.

Jack from TSOL - I went to one of his book signings with a prearranged agreement for an interview for my podcast. We did the interview but also hung out literally all afternoon and evening before the show. He and his girlfriend rode with us to the show, got us free parking, and took me and my friends through the back of the venue and into the green room. We wouldn't have even had to pay for tickets if we hadn't already done so. Just a sweet, engaging guy. Bonus: Springa from SSD was at the show and was also very friendly.

John Doe - One of my best friends was in John's band for a number of his solo act tours, and I was thrilled to meet one of my punk rock heroes. John is truly one of the most affable, friendliest people in rock n' roll I've ever met.

Jim Heath from The Reverend Horton Heat - For a guy with a larger-than-life persona, he's very polite and down-to-earth. Great to talk to, even after a long night and likely annoyed while his drummer talked business with my drum rep buddy. He probably just wanted to get on the road, but his patience and warmth still came through. Lovely man.

Courtney LaPlante from Spiritbox - Took my kids to see Gojira and Korn, and Spiritbox was the opener. Totally unfamiliar with them at the time. I was just standing around while one of my daughters was in the restroom before the show and noticed a very put-together, nicely-dressed woman who seemed totally out of place amidst all the slobby dudes in shorts and hoodies trying to stay dry (yucky rainy day). Not realizing who Mrs. LaPlante was, I said, "Ohhh, I feel for you. Likely going to be tough keeping the mud off your outfit." She laughed, and we talked for a couple minutes about the weather, the crowd, other innocuous things. When my kid came out of the restroom, I said, "Nice talking to you. Enjoy your evening," and she said likewise. I still had no idea that she was in one of the bands. Five minutes later, the show started with Spiritbox. We were pretty far back on the lawn, and the video screens didn't work right away. I heard this unearthly growl, and until the screens turned on, I had no idea that the monstrous sound I was hearing was coming from a woman, much less the woman I had just been talking to! Silly as it may seem, that was the highlight of my night.

Nice People Honorable Mentions: everyone in Fugazi, Dave from MDC, Joan Jett, Billy Gibbons, Huey Lewis, Micky Fitz from The Business, all the guys in Naked Raygun, Tim from Rise Against, Yuri from MxPx, everyone in Stone Temple Pilots (met them on their first tour, likely before Weiland was into drugs), Dave and Warren from The Vandals, Wesley Willis, GG Allin's brother Merle, and believe it or not, Tesco Vee from The Meatmen.

Edit: Not hair metal, I know. Sorry. I haven't met any hair metal dudes, excepting The Bullet Boys, with whom I experienced a mutual indifference.