It was Korn for me. My friends sister bought Life is peachy and I heard Good God, and that was it for me. Wanted one ever since then. I liked Wes Borland as well, but he actually had his 6th AND 7th strings tuned to C# most of the time. But korn....say what you want abut them... but that tone has stuck with me for years.
I got my first 7 string in high school. it was a musicians friend special ESP LTD MF-207 ( it was an F body with the skull inlays) Second was an RG7620 (this was the model Korn used touring quite a bit, other than their UV's)I told myself in 98 that I would own one.. and i FINALLY had one!! That was in 2010. Last Year, I bought a brand new RG7420. It is pretty cool. Tuning stability is better than the 7620 (probably had damaged knife edges). I upgraded the bridge pickup to a blaze neck.. and now i think I am in love. haha
ANYWAY... Long story short... KORN!!! (Supposdly even Steve Vai was blown away by what he heard them do with them)
For me it wasn't once person, I always had this thing where I would just reach for or hear lower notes that were not on the neck of a standard or dropped tune guitar.
I think when I got into Nile I really wanted one to do drop A, so I guess you could say it was Nile. Funnily enough I don't really play drop A at all now.
I think what sealed the deal for me was Dave Weiner
because he didn't just do chuggy metal stuff. I Was like 'Wow, you can do other stuff on a seven?' I mean, objectively I knew you could but until you hear it you're always a little skeptical.