First off, glad I wasn't the one who started this thread...

Second, with DS9, I have to go season by season, just like with TOS & TNG, though just about any Odo-centric episode (aside from 'A Simple Investigation') is worth watchin', just 'cause its Odo-centric.
And third, my season by season breakdown of favorites! Since my DVDs aren't handy (I have the first three seasons), I'm havin' to use StarTrek.com's episode guide...
- 'Emissary', 'Captive Pursuit', 'Progress', 'Duet' & 'In the Hands of the Prophets' (first DS9 episode for me) -
- The Circle Trilogy ('The Homecoming', 'The Circle' & 'The Siege'), 'Necessary Evil', 'Blood Oath', 'The Wire', & 'Crossover' -
- 'The Search, Parts One & Two', 'Defiant', 'Improbable Cause / The Die is Cast' & 'The Adversary' -
- 'The Visitor', 'Homefront / Paradise Lost', 'Crossfire', 'To the Death' & 'Broken Link' -
- 'Trials and Tribble-ations', 'Rapture', 'The Begotten', 'Children of Time' & 'Call to Arms' -
- 'You Are Cordially Invited...', 'Far Beyond the Stars', 'Inquisition', 'In the Pale Moonlight' & 'His Way' (love this one!) -
- 'Take Me Out to the Holosuite', 'Treachery, Faith, and the Great River', 'Chimera', 'Badda Bing, Badda Bang' & 'What You Leave Behind' -