4) Bug
One of the character’s conspicuous for their absence in the big screen Guardians line-up is Bug. The insect-alien was one of the main members of the proto-Guardians team from 2007’s Annihilation: Conquest and, though he isn’t a founding member, he did later join the group proper.
In the comics, Bug is kind of the third wacky, oddball character after Rocket and Groot, as he brings a lot of humour to the team. That’s not something the current line-up is lacking, of course, but there’s still definitely a place for Bug somewhere in the ensemble.
Unfortunately, we might be hoping in vain with this one. James Gunn has admitted before that he wanted to put Bug into the first Guardians, but 20th Century Fox currently have the rights to the character. Still, let’s hope something can be sorted out in the near future. After all, it’s not like Fox are using him at the moment.