5. Ms. Marvel
Ms. Marvel (Carol Danvers) is a hugely powerful character who is strongly associated with the Avengers and who has long been rumoured to be making an appearance in the Marvel Cinematic Universe. A blonde bombshell, Ms. Marvel was an officer in the United States Air Force when she was caught in the explosion of a Kree device (the Kree being an alien race in the Marvel universe) and resurfaced later with superhuman powers. The powers she gained included flight, superhuman strength, speed, stamina and durability, as well as the ability to project and absorb energy and she became a very prominent heroine both as a member of the Avengers and whilst flying solo. She's an essential character, as far as I'm concerned, and has to be brought to the MCU soon and her costume would go down a treat with the male audience, especially if she was played by an inevitably gorgeous actress. She has actually been touted for an appearance for some time, with some people thinking she'd appear in the Avengers sequel. That doesn't look likely to happen, however, but she should definitely appear in the future.