For me, it's a three-way tie: "Sacrifice of Angels," "Way of the Warrior" and "Siege of AR-558." I also love Garak and Worf duking it out on the Defiant in "Broken Link." Garak is usually a little too sophisticated for bare-knuckled fisticuffs, so seeing him go toe-to-toe with Worf and hold his own was pretty exciting. Kira and Jake's Mortal Kombat LARPing was certainly a unique DS9 moment.
My only regret in that scene is that they didn't draw more parallels to Sisko losing the Saratoga at Wolf 359. They could have had a brief flashback to Jennifer's death when the bridge was on fire, and they should have definitely showed Sisko getting jostled in the escape pod as it launched, like in the beginning of Emissary.
I can see why they didn't, though. He had moved on from her death, which was the point of the pilot. Couple that with how he was just the XO on the Saratoga, while he was the captain of the Defiant. Plus, he helped design and build her. He had a far deeper connection with this ship than at Wolf 359. (Speaking of the ship itself. Obviously, losing Jennifer was a major life change for him. But like I said, he already moved on from that.)
I'm going with "Way of the Warrior". It had everything: ship to ship, shop to station, phaser blasting, and hand to hand with sharp objects.
The first battle of DS9 in "Way of the Warrior," when the Klingon fleet fires on the "toothless old Grishnar cat" and discovers it has a few teeth left. Followed by hand-to-hand combat on the station.
That battle has an advantage most others don't... we already know the outcome going in, which is a massacre. It allows us to connect a little more quickly with Sisko because it's very obvious something life-altering will happen there. I think this helps with the overall battle sequence.
The battle in The Jem Hadar is my favourite battle in 24th century Trek. Everything leading up to that point is about putting you off, like all their knowledge of the Alpha Quadrant and how easily they walk through forcefields or the reveal that they've been wiping out ships and colonies in the GQ. You have only the third Galaxy-class starship ever shown appear with a captain in TNG red acting all Picard like. The ship looks beautiful as it emerges from the wormhole and then soonafter charges toward the planet where Sisko and Quark is being held. The battle starts and the Odyssey is immediately overwhelmed and all these dinky runabouts can do is barely get out of the way. Eventually the bridge is on fire and the day is saved and then the Jems go and kamikaze the sister ship of the Federation flagship just to make a point. This still had the feeling of TNG where 40 ships getting wiped out was a serious blow to the Federation fleet. I will always love these small moments with focus on one or two ships over big battles with a faceless armada.