I tend to blend my h/c and fluff so some fics might be more whump-heavy and less light in tone then you're looking for, OP, I hope that's okay?

Sam/Gabriel

Intercession (https://www.fanfiction.net/s/9601582/1/Intercession) -- annamoore
"Do you pray to the angels as well?" The priest had asked. Sam's face scrunched in confusion.
"I thought you were only supposed to pray to God?"
"You can pray to God, and Jesus, and Mary, and all of the angels. They will listen, and they will help you, and all of them love you."
[In which Sam has spent his entire life praying to the Archangel Gabriel.]

Being Human (http://wolfish-willow.livejournal.com/56463.html) -- wolfish_willow
When Sam's caught in a trap set by Eve and told he's one of her children, he's hurt and tired and doesn't know what to believe. Thankfully, he's also got a certain Trickster angel looking out for him.

Still Standing (http://vlbuehle.livejournal.com/9888.html) -- vlbuehle
S6. Dean's been abusing Sam when drunk. Gabriel finds out.

Sam/Castiel

The Importance of Cuddling (https://archiveofourown.org/works/3997051)
Cas realizes Sam never asks for anything, even if he might need things.

To Forgive, Divine (http://fandomcorner.livejournal.com/71654.html) -- fandomcorner
Sam is upset. Castiel tries to find out why.

Betrayal (https://www.fanfiction.net/s/6668001/1/Betrayal) -- supercellchaser
"Zachariah was growing impatient. He had a job to do and Dean Winchester and his abomination of a younger brother were causing quite the amount of trouble for him." (supercellchaser has actually written a fair bit of really satisfying Sam/Cas h/c so you should check them out.)

The Other Guardian (http://ladybastet92.livejournal.com/79430.html) -- ladybastet92
When Sam goes missing, Dean isn't the only one who worries. "Alternately, the summary of this fic could be: "Where Cas is uber-protective and Sam gets whumped a lot".

Wishing Is Cold This Year (https://www.fanfiction.net/s/8089591/1/Wishing_Is_Cold_This_Year)
Dean has his head rather determinedly up his ass, so it falls to Castiel to take this one. Post 5.03ish. [This is genfic, but heavily Sam-Castiel centric, and also less light and fluffy, but I quite like it so maybe worth a look if it's your thing?]

This is awesome, thank you!