Gibson Les Paul Deluxe. I sold it and bought a Kramer Pacer (1985?).
At the time, it was a Les Paul, and many classic players played them, so it should be good, right? And when I look back, I think "I sold a Les Paul to buy a Kramer?" But the truth is that the Kramer was a far better guitar than the LP.
The Lp had some severe finish proplems, but I didn't care about that at the time. It had the metal covered humbuckers -- just like the PAFs that EVH had used. Well, no, they were minihumbuckers. I thought something looked out of proportion when I bought it but something didn't quite click. It wasn't until later that I realized that it had mini humbukcers and that is why it sounded so thin.
But it's an LP, so it should play great, right? Well, I was read Guitar Player (or a similar mag) on how to set up your guitar. I popped off the truss rod cover only to find that the truss rod bolt was broken off. OK, so that was why it played like crap, and the minihumbuckers made it sound like crap.
The Kramer was a huge upgrade. But still, to this day, despite what I know about my old LP Deluxe, I still wish I had it. At least for a day. I'm sure after a day of fiddling with it, it would confirm that I made the right choice back in 1985 when I was 15. But, there is still that lingering doubt.