If there's one thing you know about the MCU — even if you're not a huge fan of the movies — it's that there are a ton of characters. The posters can hardly contain them all. But, the Avengers included in the movies are actually only a small fraction of what exists in canon, if you look at all the characters that have technically been Avengers in the comics. The Avengers were first formed all the way back in 1963, and since then, members have come and gone. I'm talking a lot of members.
A list of all of the Avengers ever can be found on the Marvel Wikia site, along with information about their current status in the comic book world, and when and how they joined the superhero supergroup. (Comic Vine also has a more concise list that leaves out honorary members.) But while there are a ton of names here — including plenty of sub-groups like the Great Lakes Avengers and the Avengers Academy Students — there are some that standout for comic and Marvel Cinematic Universe fans, either because they should be included in the MCU eventually or because it's believed that they never will.
Here's a look at a few of the Avengers who haven't made the leap to the big screen.
Rick Jones has been around since the start of the Avengers. He was the one who was originally (accidentally) responsible for Bruce Banner becoming the Hulk when he was a teen trespassing on a Gamma Bomb testing site. He was also the one to bring the original Avengers together. On top of that, he has also appeared as the second Bucky and a character named A-Bomb. An article on The Hollywood Reporter argues that Rick would serve as "an audience avatar" if he joined the MCU. It also calls him "one of the most important comic book players never to appear in a movie".
In the new Captain Marvel movie, Carol Danvers' best friend is Maria Rambeau, and she has a daughter named Monica. Well, in the comics, Monica becomes a superhero herself and is also a version of Captan Marvel. But, in the latest comics, she is going by the name Spectrum, which could potentially allow her to appear alongside the current Captain Marvel, played by Brie Larson, in a MCU film.
Yes, Hercules is an ancient mythical hero, but he's also a Marvel hero, first appearing in the books way back in 1945. Nerdist notes that it's possible Hercules didn't already join the franchise because of similarities between the character and Thor, but with Thor potentially leaving after this phase of MCU movies, it could be Hercules' time.
Black Knight, aka Dane Whitman, was first introduced in 1967, and according to the Marvel Wikia, "served several tours of duty with the Avengers." CBR reported in December that there was a rumor that character would be joining the MCU, but that it was totally unconfirmed. Then, in January, Newsarama put forth the idea that Black Knight would show up as a surprise in Avengers: Endgame based in part on the re-release of some old comics that feature him and hypothesized that he could be introduced via the Quantum Realm, which some fans believe the Avengers visit in Endgame.
Her name is Jennifer Walters, she's Bruce Banner's cousin, and she made her first appearance in 1980. According to a Cinema Blend article about heroes Marvel should add to the MCU, "[She-Hulk] has made a name for herself as a strong (figuratively and literally), positive and humorous female character, and has served on teams like the Avengers and Fantastic Four."
Again, these are just a few of the many current, former, and sometimes Avengers out there. This world is pretty much endless, but, hey, the movies probably are, too.