Like most serious chess players I've tried out a number of different openings over the years, for a number of different reasons; educational purposes, competitive surprise, because I bought the book, even at times just because I wanted some variety.
For tournament games, in response to 1. e4 I went e5 at the beginning of my career in the early 1980s, tried the French Defense (1. e4 e6) a few times with a lot of suffering involved, back to 1... e5, a mixture of Sicilians (1. e4 c5) and the Pirc/Modern (1. e4 d6) for much of the 1990s and early 2000s, then about four years ago started working with the Center-Counter (Scandinavian) 1. e4 d5, which I have played pretty consistently since.
Notice the one main defense that's not listed? That's right, the Caro-Kann (1. e4 c6).
Why not the C-K? Hmm, before reading further you need to click this link...
Now that doesn't represent my real feelings about the Caro-Kann defense, but it's funny, I think I did play it exactly once in all my tournament career, and lost to Darcy Robinson. One loss did not completely determine my attitude toward the C-K, but generally I saw it as passive and somewhat dull. Botvinnik took it up in his later years, when he was old. A pretty consistent King's Indian Defense man against 1. d4 since my early days, I just always figured the Caro didn't suit my supposed style.
A few months ago I gave it a try in some blitz games, mainly for the variety factor mentioned above. I don't even have the one book I own on this opening available (in storage until early May) and so after the first few moves I was basically on my own, just making stuff up, developing pieces and trying to control the center. And guess what? I did fine. I scored pretty well, and the games didn't seem dull in any way. Of course it was blitz, where there's rarely a dull moment, but I began to think the C-K is OK!
After a brief period it occurred to me (I'm sure this is hardly an original insight) that the Caro-Kann is just an improved Center-Counter! WOW! I don't know why I never noticed it as a dedicated Center-Counter practitioner, but after 1. e4 c6 Black can play d5 on move two against anything, and maintain his full and fair share of the center.
So after all these years (going on 27 of tournament play) I finally have some appreciation for the Caro-Kann. Once I actually start learning some book lines, who knows how far it might take me?
Want to be taken somewhere else? Take the "A" Train. But make sure you have the full 9:26 available. This is just magical stuff (h/t Jaltcoh):