Ornstein and Smough down! God, that fight, at least the first round, is like the absolute best and worst of this game in one crazy package. Lack of sound cues, inaccurate hitboxes, messed up AI behavior, the necessary reliance on that terrible auto-centering camera, and yet the fundamentals of the fight are solid enough that things often just work anyway and produce huge thrills. There's synergy between them, even though it seems like they operate completely separately, so it's just a product of the design of their movesets. Dodging simultaneous attacks perfectly with the barest of margins is amazing. Having Smough do his bulldozer move three times in a row or hitting you with an invisible hitbox that extends past his hammer model, or having Ornstein attack silently from across the room or do that whole flying rush attack-standing animation-sudden flying rush attack finish thing (seriously, that must have been straight up unfinished, it's far too obviously disastrous to be intentional) makes me want to break things. But it was so damn satisfying in the end. It's hard to explain, but I'm sure veterans understand.
I guess I'll hit the Duke's Archives next. I'm not a big fan of that area at all, but I'm expecting some seriously devious black phantom placements there. O&S were my biggest fear coming into this run, and the game starts to peter out a bit at this point anyway, but hopefully those phantoms will keep things interesting without just breaking the game.