For me, it's always Bucky being overwhelmingly grateful to be able to spend the holidays with the Wilson family with all the fluffy family feels, but I feel like that's the most obvious one. So another headcanon I love to think about is if some group (the og avengers or just Sam, Joaquín and a few people) did a Secret Santa and that goes one of two ways. Bucky either threatens every person until he finds who got Sam and demands they switch so he can have Sam. Or he finds out who got Sam and gives that person the most intimate, personal, extravagant gift to give to Sam and refuses to admit it's from him.