Here are my (sort of, maybe, it shifts every hour really, but I think I've settled on these) current top (not necessarily in order) 9 (there were going to be more but I got tired) Leslie Knope/Ben Wyatt fic recommendations.
Fandom Category: Parks and Recreation
Pairing: Leslie Knope/Ben Wyatt
Fic Title: Beautiful Mess
Rating/Warning(s): PG-13, some language
Genre: Romance, Fluff
Why This Must Be Read: Favorite, favorite, FAVORITE. Ben goes back to Indianapolis after the Harvest Festival, but he and Leslie keep in contact through phone calls, texts and e-mail, maintaining the delusion that they're just friends until it gets shoved in their faces that they are in fact in a long distance relationship, even if they didn't realize it.
This is so wonderfully in character, from the way their separation is quietly killing them both, right down to the hilarious way these two dorks manage to bumble into their happy ending
Fic Title: The Art of Looking for Trouble
Author(s): annakovsky and tearupthesky
Rating/Warning(s): NC-17. Sex.
Genre: Humor, Fluff, PWP
Why This Must Be Read: A pitch-perfect, hilarious Leslie voice. Set mid 3x01 "Go Big or Go Home", after they crash Chris and Ann's date, Leslie and Ben get drunk and bicker their way into great sex, while Leslie tries to figure out why she's having so much fun with a guy she thinks she hates, and Ben does his best to show her that there's a human being under the "Mean Ben" exterior.
Fic Title: All Roads Lead to You
Rating/Warning(s): PG-13, mentions of non-graphic sex
Genre: General, Angst, Fluff, Romance
Why This Must Be Read: Ben and Leslie have a connection long before they ever meet. A perfect entwining of their backstories, they parallel and shape each other's lives for years before Ben ever sets foot in Pawnee, growing together without ever knowing it, until by the time they finally get it right it's ridiculously sweet and fitting.
Fic Title: Stay
Rating/Warning(s): PG-ish for language
Genre: Romance, general, fluff
Why This Must Be Read: Ben gets the call that he's being sent back to Indy, and decides that - if she'll have him - he doesn't want to leave Leslie. It's a common plot in early L/B stories, but perfect characterization and strong voices set this one apart, as Ben thinks about the ways Leslie has changed him, and Leslie thinks hard about what it means that he wants her to choose whether he should stay or go.
Fic Title: Crash and Burn
Genre: Angst, Romance
Why This Must Be Read: Ben is headed back to Indy, he realizes he doesn't want to leave Leslie... and she turns him down. For couple this fantastic, to NOT fall into each other's arms during that silver screen-esque climactic kiss under the stars is a shock, and Ben is understandable destroyed after putting himself out there. They work it out in the end (I'm not big fan of unhappy endings) but how they get there is worth a read.
Fic Title: The Whole Sky Fell
Rating/Warning(s): PG-13/R, language
Genre: Angst, Drama, Romance
Why This Must Be Read: Leslie/Ben is an understandably sweet and fluffy ship - cotton candy and whipped cream covered waffles are staples of the show, let alone the fic - so when a story like this comes along it's a revelation.
His father dies the day before the harvest festival is the summary and first line, and it sets the tone all the way through, as Ben flounders through saying goodbye to a man he knows he disappointed, in a place he hates, holding onto Leslie and the possibility of the happiness she represents like a lifeline.
Fic Title: May, She Will Stay
Genre: General, Romance, Fluff
Why This Must Be Read: Leslie and Ben stick together through April and Andy's wedding reception in 3x09 "Fancy Party", with drunken banter, disgusting vegetable loaf, Jerry's untimely interruption, pizza and slow dancing, and it is unspeakably perfect.
Fic Title: Wall Flowers and Hamburgers
Why This Must Be Read: A great little possibility for the conversation at the end of 3x10 "Soulmates" that we saw but didn't hear, with wonderful callbacks to Leslie's questions for Tom on their date, and Ben's corresponding correct answers. Does a really nice job of showing how good the two of them are together, and how much they hate the rules keeping them apart.
Fic Title: I'll Tip My Hat to The New Constitution
Genre: Romance, Fluff
Why This Must Be Read: SECRET DATING ESCAPADES. The subtitle is (or Five Times Ben Took Leslie On a Secret Date, and One Time He Didn't).
This is the very first P&R fic I read, and boy am I glad it was. So so stupidcute and sweet. There are calzones and parrots and Star Wars. Super short and adorable.
I've barely scratched the surface of the great fics in this fandom. Check out all the authors I've linked here, and leslie_ben for more.