You've got loads of great recs already, so I'm just going to add two of my favourites on here:

Sam, Son of Adam (http://maychorian.livejournal.com/30950.html) - maychorian
"I don't…I'm not…no throne, no," Sam protested. His voice sounded utterly weak to his own ears, though, and so very easy to ignore. "I just want my brother." [Narnia crossover. Starts off with cracky undertones, but then things get intense.]

Take a Long Line (https://www.fanfiction.net/s/3400565/1/Take-a-Long-Line) - Derry
Winchester isn't stupid. Dangerous, unpredictable and often reckless. But definitely not stupid. So there has to be a good reason that, knowing full well that he's on the FBI's radar, Dean Winchester brazenly walked into a Federal Building. --[Numb3rs crossover. Really great outsider-POV of the dynamic between the brothers.]