"The thing I loved most about Parks and Rec is that it made you feel good while making you laugh. It was just...nice, which really stood out in a time when lots of comedy is being mined from awkward moments and cynicism." -Uproxx
That about sums it up.
Parks & Recreation was a rare breed of television where the big 'event' episodes were just as good, if not better, than the smaller-focused ones. I tend to prefer the latter because the former usually tends to try too hard (X-Files' "Jose Chung" over the mythology episodes, for instance), but everything from multiple weddings to the Harvest Festival and Unity Concert to Leslie Knope's election all paid off perfectly. This is due, I believe, to such wonderful characterization that it is the most glorious joy to see the cast come up Millhouse.
Despite this, I usually claim season 2's "Telethon" is my favorite episode of Parks & Recreation (though the simple sweetness of "End of the World" and "Leslie & Ben" probably latch them closer to my heart). "Telethon" was the episode I first returned to after the disappointing series premiere, and it's been one of my favorite shows ever since. It was also the first episode that truly tied the world of Pawnee, Indiana together with its delightful cavalcade of minor supporting characters rivaled only by The Simpsons (my favorite being Barney the accountant). And it had the cutest opening ever.
Anyway. The show is over and that's sad and here are my favorite episodes.
Season 2, Episode 2 - "Stakeout"
Season 2, Episode 22 - "Telethon"
Season 3, Episode 7 - "Harvest Festival"
Season 3, Episode 9 - "April & Andy's Fancy Party"
Season 4, Episode 4 - "Pawnee Rangers"
Season 4, Episode 6 - "End of the World"
Season 4, Episode 22 - "Win, Lose, or Draw"
Season 5, Episode 14 - "Leslie & Ben"
Season 6, Episode 21 - "Moving Up"
Season 7, Episode 4 - "Leslie & Ron"