Here are a couple of Brokeback Mountain SPN video trailers that are great:
Brokeback Supernatural (http://www.youtube.com/watch?v=x3hxjq7AExo) Wincest
Brokeback Mountain Supernatural Style (http://www.youtube.com/watch?v=-hB9CVVXCN4) Wincest
I haven't read these so I have no idea what they're like. It's Destiel Once Upon a Time in the West (https://www.fanfiction.net/s/7976331/1/Once-upon-a-time-in-the-West)
Siyo Nqoba (We’re Going to Conquer) (http://grogngrub.livejournal.com/19002.html) - The Lion King by arglikeapirate
Deadsville (http://unreckless.livejournal.com/95805.html) - Brokeback Mountain by unreckless It's f-locked but you could always try a friend request.
Infidelity fics
What Should Have Been and Nearly Wasn't (http://blynnk.livejournal.com/98864.html) by blynnk
Sweet Dreams Remain (http://fourfreedoms.livejournal.com/145361.html) by fourfreedoms
A Devil to Help Me Get Things Right (http://doodle-writes.livejournal.com/23394.html) by doodle_writes
If I Only Had All of You (http://j2-ficwhore.livejournal.com/20409.html) by j2_ficwhore
Here is a bunch of stories where they are caught or overheard having sex
J2 Recs - Caught Having Sex (http://j2-recs.livejournal.com/97414.html)
That should keep you occupied for a while :)

Deadsville isn't f-locked everywhere. It's linked from my masterlist which is the post at the top of my journal. This takes you to my fic journal likeanything where it's unlocked. It's also on AO3.

Oh excellent! Thanks for letting me know :)

Fantastic infidelity fic that I've read twice already but they are not cheating on each other. Also the angst is unbelievable, so definitely worth a read...
Damage (http://dimeliora.livejournal.com/36658.html) by dimeliora
Summary : Jensen Ackles has the perfect life. He's the governor of Texas, happily married, and has an incredible daughter. Everything is fine, until his little girl brings her new boyfriend home.