Ooh. Nice topic!
Uh... Def Leppard. I was a huge fan of them up to and including Pyromania, then ... I stopped. I know glam metal doesn't get a lot of respect, but it was my gateway drug into the heavier stuff and Def Leppard was ... a lot of my youthful turn into a metalhead.
Saxon. They were my stepping stone from glam metal into the harder stuff, together with old Black Sabbath. Unlike Black Sabbath, however, which has remained on my playlist almost constantly—rarely does a week go by without me dropping a Sabbath album into the headset—I hardly ever listen to Saxon any longer.
For something a bit more modern, Gloryhammer. Absolutely hilariously fun power metal cheese that I enjoyed like crazy ... and then stopped after the shenanigans with their lead singer. I followed the lead singer as Angus McSix later, but simply stopped listening to Gloryhammer because the whole situation left a bad taste in my mouth.