Honorable Mention: Pete Wisdom
This one is technically a bit of a cheat. Pete Wisdom first became a member of X-Force during 2000 when writer Warren Ellis was given the task of editing three of the X-Men spin-offs, including X-Force. Ellis wrote the first story-arc for each book, setting the tone that each series was to follow. For X-Force, this meant bringing back his creation from his Excalibur run, Pete Wisdom. Pete Wisdom is a mutant who possesses the ability to fire white-hot plasma knives from his fingers. Hes a chain-smoking, quick-witted British spy who has worked with numerous intelligence agencies, including MI-13 (basically the British version of SHIELD). When Ellis wrote Excalibur in the mid-90s, he created Wisdom for that group and had him hook up with Kitty Pryde (and he also had Colossus pummel Wisdom). After Ellis left, Wisdom drifted into obscurity. But during Ellis tenure on X-Force, Wisdom briefly led the team, joking about how they should start calling him Professor W. Although his tenure on X-Force was short-lived, Pete Wisdom is a great character and could serve as a bridge between the different mutant movies if Fox does indeed intend to branch out into the larger X-verse. He could be for the X-Men what Phil Coulson has been for the Avengers, working for a government agency or Professor Xs Mutant Underground that has been established (but often unexplored) in the comics.