In hindsight, he shouldn't have said "Gabriel, don't you dare" because, really, when has Gabriel ever turned down a challenge?
The shorter man (Trickster? Archangel) hadn't even done it on purpose; at first that is. It was just a simple poke into the hunter's side; a small, little, annoying gesture of camaraderie. But the moment an unmanly squeak fell from Sam's lips, his body inadvertently jerking away from the offending finger, he knew he was fucked. Eyes widening, he could only watch in mounting horror as smirk began to grace Gabriel's face. "Oh," the man murmured, "This is going to be fun."
Then of course, Sam tried to tell Gabriel (the fucking Trickster at this moment) to not do something, and well, in the end, he made it worse for himself.
Rule #1 on how to deal with Gabriel: Don't tempt him with something he shouldn't be doing.
Bad Sam.
Very bad Sam.
He glanced at the door, trying to judge how many seconds it would take to make it across the room but before he could even lift a foot to run, he heard a snap and suddenly found himself on the bed, a heavy weight plopping down on his stomach like it owned the joint. Legs straddled his hips, trapping his arms between them, as Gabriel smiled down at him with all the sweetness he shouldn't have at this moment of sheer terror.
"Now, Samshine, did you really think I would let you go that easily? After learning about this deliciously juicy little tidbit?"
The hunter struggled, completely in vain. "Now, Gabriel, I swear- I swear, if you do this-just don't do this! I don't know how, but I'll get you back. Are you prepared for the consequences?"
"Hmm," was all the Trickster said, followed by a long pause, as if he were thinking about it. Sam's mind was yelling in relief 'yes, yes, it worked!', his body slowly relaxing when suddenly, the man above him attacked, fingers mercilessly digging into his side.
Hysterical laughter reluctantly poured from Sam's mouth as he tried to squirm away from the onslaught of torture, body twisting and turning and bucking in attempt to escape from Gabriel. Unfortunately for Sam, the strength of a human was absolutely no match for the strength of an Archangel.
"G-G-Gabr-riel! St—haha, stop!" He laughed, tears coming from his eyes.
There wasn't even a pause when the shorter man responded in absolute delight. The fucker. "Now, why would I do that, Sammy-boy? If I had known that you were ticklish, maybe I might have joined this little rag-tag team of misfits sooner. This is great!
He continued over the squirming and maniacal laughter beneath him. "This is one of the things Daddy-dearest got right with you humans; ticklish little bodies. Poor, poor Samsquatch, whatever will you do?"
The hunter opened his mouth, about to give Gabriel a piece of his mind, but all that came out was another round of laughter.
'Gabriel! Gabriel, please, no more! Mercy, uncle, whatever!' he frantically prayed.
Said being gave a huff, eyes twinkling with mirth but mercifully, so mercifully, pulled his fingers away from the twitching human and the torture finally ended.
The laughter was slowly dying away but a smile stayed firmly planted on Sam's reddened, blotchy face. His chest heaved up and down and his mouth parted to say something when the door slammed open. Dean froze at what could only be assumed as a promiscuous sight; Gabriel perched on top of Sam, Sam breathing heavy, face bright with exertion.
"What the absolute fuck is going on here?!"
At the sight of an overprotective, completely possessive older brother, Gabriel gave a low whistle. "Whelp, I hate to scoot and skedaddle, but you know how it goes; places to be, naughty humans to punish. Tootles, big boys."
With a snap, the Archangel vanished followed by a hearty bellow of "Gabriel, you little shit! Get your feathery, brother-molesting ass back here!"
All Sam could do was laugh some more.