Try An Itch You Can't Scratch (http://meus-venator.livejournal.com/50370.html) by meus_venator.

Original Prompt: Dean and Benny have been travelling through Purgatory for months now. Nerves are getting frayed and Benny senses a growing strain between them. Benny knows he will have to address it soon, it's starting to affect Dean's performance in fights. When they come across a lake, Dean orders Benny away so he can have some alone time and get cleaned up. Reluctantly Benny obeys, and heads out to guard the perimeter. Somehow Leviathans get a hold of Dean and are dragging him trussed up like a Christmas turkey back to Dick Roman. Benny rescues the still bound Dean and drags him into a nearby cave. While the remaining Leviathans comb the area looking for the men Benny teaches Dean a lesson.

sounds fun, can't wait to read! thanks :D

Becomes A Monster (http://runedgirl.livejournal.com/63320.html) by runedgirl
Sam's “normal” life dissolves when his brother mysteriously returns from the dead. But when Dean came back, Benny the vampire wasn’t the only thing that came back with him. Now Sam is in a race against time to save his brother. This is one race that Sam refuses to lose.

The Lines Between Brotherhood and Blood (http://jasmineisland.livejournal.com/20659.html) by jasmineisland
Takes place after Southern Comfort, S8. The Vengeance Specter laid open wounds between the Winchester Brothers. A hunt goes wrong, which only deepens the divide. Just when Dean begins to feel like moving on and splitting up might be the best answer, a Pagan God drags Sam into a mission of absolution that he won't refuse. Dean discovers that his brother has been hanging on by a thread, and the year he was in Purgatory was much worse on Sam than he ever suspected. Cas, Benny, and, worst of all, Crowley see what he has somehow missed -- just how fragile Sam is. With a little help, Dean learns what Sam had been unable to share -- just how far he was willing to go do and what he is still going through, proving to Dean that he is still Sam’s stone number one.

Both Sam/Dean as a main pairing but have past Dean/Benny
xxx

thanks so much! I'd already bookmarked "The Lines Between..." but I'm glad to have some one else rec it.

alexadean writes some of the best Dean/Benny I've read

Here on LJ See her master post or over on AO3
O' Sailor, Why'd You Do It?
I Got the Love That Keeps Me Waiting
Heart Made of Parts
On the Bound

: )

thank you for the recs! *off to read*

"... but any other category is ok". Well, this one is GEN: O Brother, Where Art Thou? by emebalia.
Summary: "This human was probably my only chance to get out of Purgatory. Better not letting him get killed." Dean and Benny in Purgatory, Benny's POV. Warning: A vampire's mind is a dark place.

https://www.fanfiction.net/s/9295349/1/O-Brother-Where-Art-Thou

I'm a huge fan of canon Benny and there really isn't anything I'd change about their relationship except how "short lived" - in a sense, it is. That's why I definitely don't mind reading fics involving the two of them. They're awesome together. GEN is ok. Thank you!