No. 7: Captain America & Falcon
Credit: Marvel Comics
A partner and sidekick to Captain America, Falcon (Sam Wilson) and Captain have always had each other's back, making this one of the oldest bromances in Marvel history. While they're origins and pasts have been changed and recreated many times, (changed for the MCU too), these two never stray far from each other. Falcon has even recently taken over the mantle of Captain America after his age caught up with him just as Bucky did not to long ago. Which makes sense since Falcon was trained by Captain America himself. Recently this bromance has taken new heights with the reveal of Sam Wilson in The Winter Soldier a couple years ago in the MCU movie.
Even more so than Bucky in recent years, Falcon has been Captain America's most constant companion.