SamBucky

Winter Falcon is the slash ship between Bucky Barnes and Sam Wilson from the Marvel Cinematic Universe fandom.

Canon
Bucky and Sam became were close allies when fighting during the accords and had encountered each other when Bucky was still in the hands of HYDRA,

Captain America: The Winter Soldier
Steve, Sam, and Natasha had kidnapped Jasper Sitwell, one of the undercover HYDRA agents working for SHIELD, and had taken the freeway when they encountered the Winter Soldier, who threw Jasper out of the car into a passing truck, killing him. Before the Soldier could assassinate Steve and Sam, Sam immediately pushed down on the brakes, resulting in the Winter Soldier getting thrown off the car.

This did not stop him, however, as he slowed himself down with his metal arm before charging back at the car and ripping out the steering wheel, causing the car to lose control and crash. Everyone got out of the car before Winter fired a grenade launcher, which Steve took with his shield, sending him plummeting into a bus below.

Winter then targeted Natasha, who eventually temporarily disabled Winter's metal arm and strangled him. Soon, Winter was close to eliminating Natasha, but was saved by Steve, who fought Winter.

After it is revealed that the Winter Soldier is Bucky Barnes by Steve, Winter is left confused and attempts to shoot Rogers, but is quickly kicked down by Sam when he flew down on is Falcon suit. Winter then disappeared, a unit of STRIKE agents taking Steve, Sam, and Natasha into custody. This fails though, as Maria Hill went undercover and saved the trio.

Captain America: Civil War
After the fall of Project Insight, Bucky's encounter with Steve and T'Challa, the Black Panter, and Bucky turning back into the Winter Soldier. Sam and Bucky meet again after Steve saved Bucky from drowning.

After having small talk, the trio stole a car to meet Sharon Carter, a SHIELD agent that had recovered Steve's shield from the river and Sam's Falcon suit. Bucky, having stayed in the car with Sam while Steve and Sharon talked, eventually asked if Sam could move his seat up. Sam refused, leading to Bucky moving over a little. Steve and Sharon then share a kiss before she departs.

The trio then met Clint Barton, who had gathered other superheroes that supported Steve and Bucky. As they talked, Bucky overheard over the airport speakers that the airport would be evacuated due to Iron Man's arrival. Bucky then spread this message.

The team then went into the airport, Steve and Sam taking ground inside the airport. They then see Spider-Man, or Peter Parker, crawling on the windows of the building. Spider-Man then broke into the building to fight Bucky and Sam. After he kicked Sam to the ground, Spider-Man caught Bucky's metal arm when he attempted to punch him. He complimented on how 'cool' Bucky's arm was.

Sam then started fighting Spider-Man while Bucky threw random objects at the teen, which were thrown back at him. Bucky and Sam are then pinned to the ground by Spider-Man's webs while he mocks them. Sam then activates Redwing, who hooked onto Spider-Man and flew him out of the building, making Bucky ask if he could've done that earlier.

Bucky and Sam are eventually separated when Steve and Bucky flee on the Quinjet.

Avengers: Infinity War
Steve and Bucky don't end up meeting, but both fought in Wakanda at the time. The two both turn to dust as a result of the Decimation, or Thanos' Snap.

Fanon
Not being a very popular ship among the Marvel Cinematic Universe fandom, there isn't a lot of fanfiction compared to more popular ships, like Stucky or Stony.

On AO3, there are a total of 1,628 works. On Wattpad, there are only 66 stories with the Winterfalcon tag.

Fandom
FAN FICTION 

TUMBLR

Trivia

 * On Earth-616 both have taken on the mantle of Captain America.
 * In a promo for Avengers: Infinity War, Thor is looking through the figurines for the big battle and knocking them all down. When he gets to Sam and Bucky he says "I like those guys, they can stay".

Variations

 * Samstevebucky refers to the ship between Sam, Steve Rogers, and Bucky.