“You got a list of the nicknames available to us lesser mortals?” Sam continued, staring straight ahead at the seat in front of him. “The ‘you’re not Steve Rogers, so don’t even think about it’ collection?”
“Yeah, sure, there’s a list,” Bucky replied, pausing long enough to draw a pointed look from Sam. “Bucky,” he finished, gesturing broadly with his arm to convey the obviousness of the answer.
5 times Sam and Bucky used pet names as a joke + 1 time they used them in earnest
"Hours later, when everything was well and truly fucked, Bucky would recognize the exact moment when he should have benched himself. It had happened in the dazed split-second between Sam flashing him a smile as he swan-dived out of the plane and Bucky almost leaping right after him, his parachute lying forgotten on the floor."
When Sam gets caught in a memory machine, Bucky goes in after him.
“The first thing Sam thought when he woke up bathed in a one-inch sea of water and a soft haze of orange light was: I don’t have time for this shit.”
Or, Sam and Bucky find each other in the Soul World, and it's impossibly dull - until it's not.