For me, though there are moments which I think are better, none come close to capturing how I felt when I saw the epic Gowron/Worf fight when I first watched the show. When Worf was thrown through the glass, I was just in awe. Now yeah - I know Trek isn't exactly renown for its fighting choreography, and I've seen many, many far better fight sequences. But for some reason, in the context of the overreaching Klingon storyline, DS9, and the episode itself, that scene just wowed me more than any other.
Call me weird, but I can't say whether it was done on purpose, but I think there was a lot of cool symbolism during that fight too, particularly with that glass.
First, the camera follows the fight from the other side of the glass, and we see Gowron and Worf in combat in the background, with a pane of glass in the foreground showing Klingon ships flying into battle. Then Gowron throws Worf through it, and it shatters, in my mind symbolizing that Gowron is destroying the Empire. Then when going for the killing blow, Worf emerges from the shattered remains and kills Gowron.
I guess I could be reading too much into it, but it's cool. The only thing lacking was the music during the fight, but it was okay. It wasn't as Klingon as I would have liked.
Oh -- and I love Garek's "I'm still here, Russot" and the grin he makes afterwards. Then there are the two moments between Kira and Damar, first about his family, then after killing Russot. Great episode all around.
My other favorite moment of all time is in Shadows and Symbols when all of the plot threads of the episode got resolved -- the attack on the Monac shipyard to get Jadzia into Sto-vo-Kor, the Orb of the Emmisary, and it's subtle dovetailing into the standoff between Kretak and Kira. When Kira saw the Celestial Temple return, she couldn't care less how outgunned the Romulans had her. You can practically see her faith and confidence appear on her face. I love watching Nana Visitor act.