Necessary Evil
Whispers
Paradise
Profit and Loss
Crossover
The Jem'Hadar
IMO:
The Circle trilogy
Cardassians
Necessary Evil
Whispers (a standlone episode, but a brilliant one)
The Maquis I/II - starts an important storyline that will continue in next seasons
The Wire
The Jem'Hadar - season 1 finale - starts an extremely important storyline
also worth mentioning for one reason or another:
Profit and Loss - one of the better Quark episodes
Blood Oath - you'll like it if you like Klingons, specifically TOS Klingon characters who return in this episode
Crossover - the first Mirror Universe episode (I despised most of the Mirror episodes in DS9, but I know there are lots of other people who like them..and, after all, whatever else they are, they wre certainly fun)
The Collaborator - more Bajoran politics, occupation and religious leaders stuff
Tribunal - the annual "O'Brien must suffer" episode
