Bucky, played by Sebastian Stan, gets a good amount of screen time and the groundwork has been put in place to give Cap's former sidekick more attention in future films. First, we see him being brainwashed in a HYDRA facility and then he's apparently "killed" by a fall off a cliff. This is massively inspired by his comic counterpart's story.
In the pages of Marvel comics, Bucky first seemingly meets his end in a plane explosion. He's scooped up, however, by Russians. They then brainwash him again to become a highly trained assassin, who takes on the name Winter Soldier. Later on, when Captain America is "killed," Bucky wields the shield to take his place. In the movie, we get a glimpse of that for a quick second or so when Bucky grabs the shield and takes aim with his pistol.
