Philidor Defense: Nimzowitch variation
9)Philidor Defense: Nimzowitch variation. Coined after Aron Nimzowitch, a very interesting opening. Quite often not played anymore since white ends up with a steady edge of around +0.9. The beautiful part of this opening is that it is very forcing at the high level as white usually plays in the mainline which tends to be 10 or so moves long. So essentially you are getting into the same exact middlegame each game, if that makes sense. Although it is not played anymore as it used to since black almost always gets in a bad endgame; at least in master level games. Very niche though, not many people know about this variation.
Image credit: chess.com