4. X-Force
The only X-Men spin-off team in this list (and therefore very easy to accommodate in an already well-established movie franchise) is X-Force. The X-Force has had several incarnations and each of them have members that have already appeared in a movie. The likes of Colossus, Cyclops and Storm have all appeared in different incarnations of the team, alongside other established characters like Wolverine and some pretty awesome characters who haven't yet appeared in a movie such as Cable, Fantomex and Shatterstar. The X-Force are far more militant, ruthless and aggressive than the X-Men and it would be cool to see how that translated to the big screen (what with the peace-loving, human-tolerating, Professor X-led movie X-Men being a different kettle of fish entirely).