Brick Joke: While trying to keep Sisko conscious, Kira suggests switching DS9 to a four-shift rotation. At the end of the episode, Sisko brings up the four-shift rotation as if it were his idea. Kira plays along with it. (Sisko was probably joking, and she probably knew it.)
Quark: I thought you said you never sold "sub-standard merchandise." This was supposed to explode on impact, wasn't it?
Hanok:[beat] Maybe I should offer them a refund. [the two break out laughing]
Concussions Get You High: Averted. Sisko spends most of the episode barely conscious, with a panicked Kira trying to keep him awake.
Damn You, Muscle Memory: When Worf takes command in engineering, he notices that the control panels have been reconfigured. He tells the engineers to reset them to the standard layout, to prevent this from happening.
Fire-Forged Friends: The episode starts with Hanok ready to gut Quark like a fish. It ends with them enjoying a spin at the dabo wheel.
Good Is Boring: The Karenna have a very by-the-book method for establishing fair trade prices, based on the various production costs plus a reasonable profit margin. Quark finds their approach incredibly dull. Though he doesn't succeed in turning Hanok into a sleaze like him, Quark does get him to appreciate the thrill of a good gamble.
Improvised Weapon: Both arming atmospheric probes with torpedo warheads and the deflector dish as mentioned above.
It Only Works Once: O'Brien tells Worf that the deflector dish gun will only give one shot. Fortunately, the new-and-improved Worf only needs one shot.
It's All My Fault: Hanok sees the impending deaths of his people at the hands of the Jem'Hadar as his fault for meeting with Sisko. He even offers to make a Heroic Sacrifice to save his crew.
Locked in a Room: Bashir and Dax spend most of the episode trapped in a turbolift after the deck is flooded with gas.
Mandatory Line: Odo only appears in one scene, advising Hanok to not blow his money at Quark's.
That's an Order!: Sisko orders Bashir to seal off Deck 2 during a hull breach, even though that would mean sacrificing Jadzia. Bashir decides to Take a Third Option and seals off the deck while rushing in to save Jadzia.
Wire Dilemma: The torpedo Quark and Hanok are dealing with has two diodes - Removing one will disarm it, and removing the other will detonate the warhead. Hanok doesn't remember which is which. With a 50/50 shot, Quark throws caution to the wind and yanks one out. He chooses correctly.
With Due Respect: O'Brien says this to Worf when advising him to cut the engineers a little slack.