X-Force had a brief but memorable turn in Deadpool 2, but their live-action future may not be over yet. If it isn't, it's likely that future movies or streaming series will draw on some of the best individual issues of the X-Force comic book, which goes back to the early 90s and continued in several different volumes.
The roots of X-Force are in the New Mutants, making some of those later issues of that comic book key to the comic lore of the team. The team continued to evolve in the last thirty years, with great runs that took the darker version of the X-Men to some very grim but compelling places.
New Mutants #87
The New Mutants #87 isn't part of the proper X-Force run but comic fans will find it in most collections covering the origin of the team. That's because this landmark issue, featuring the debut of fan-favorite Cable and drawn by artist Rob Liefeld, is really where the team begins.
The New Mutants era effectively ends with the introduction of Cable, one of the first of the X-Force squad that most fans are familiar with. This issue also introduces his primary nemesis, Stryfe, and the Mutant Liberation Front, setting the stage for the X-Force book to come. It also establishes a grittier, harder tone and more graphic violence that became a signature of the series.
New Mutants #98
Another major New Mutants issue key to the foundation of the X-Force legacy is #98, which features the debut of Deadpool. This 1991 comic written and drawn by Rob Liefeld (with Fabian Nicieza also contributing to the script) pits the mercenary against Cable in a must-read battle. Though the two will eventually become one of the strangest Deadpool friendships in the comics, their first encounter is a violent and kinetic battle, with huge action that made Liefeld a rising star and led directly to the end of The New Mutants and the beginning of X-Force.
X-Force #1
X-Force #1 is one of the biggest selling comics in history, selling over five million copies, but the hype was real. The issue is perhaps the best example of the Rob Liefeld era of the book, with art and script by him that casts the team into big action scenes against a number of villains including Gideon and the Mutant Liberation Front. The issue is also significant for introducing both G.W. Bridge and revamping Warpath, the brother of Thunderbird, who had died in X-Men #95 after briefly being a member of the all-new X-Men in the '70s.
X-Force #8
Issue #8 of the first volume of the series features the debut of the Wild Pack, a key element of Cable's mysterious past. This story also advances a little of the reasoning that Cable came back to the present from the future, ostensibly for the fact that Cannonball, Sam Guthrie, would become a High Lord of great power.
Though that storyline wouldn't produce major results, the hints on the background of Cable and continued exceptional art from Liefeld made this one of the most compelling issues of the early run. This would be one of the last regular issues Liefield would pencil as he would soon leave to form Image Comics in 1992.
X-Force #60
Issue #60 of the first volume of X-Force ranks high for finally providing some answers for the origin of founding member Shatterstar. "I Know YOU Are But What Am I? (Shatterstar Saga, Pt. 2)" reveals that Shatterstar is destined to kill Mojo a thousand years in the future in one of the televised death matches on Mojoworld. The issue, written by Jeph Loeb and drawn by Anthony Castrillo, succeeds by giving fans some details while withholding others, allowing the intrigue of Shatterstar's true identity to continue to deepen.
X-Force #18
X-Force #18 is a key issue in "The X-Cutioner's Song", one of the wildest X-Men comic book crossovers from the '90s. This is a great issue for a number of reasons, including finally peeling back the layers on the strange conflict between Cable and Stryfe. The final part of the crossover reveals the Stryfe is a clone of Cable and cements the idea that Cable is in fact the grown-up version of Nathan Summers, who comic book fans of Cyclops would know as the son of Scott Summers and Madelyne Pryor. The issue ends in tragedy as Scott appears to lose his son again as Cable destroys Stryfe and himself in an explosion.
Cable And X-Force #1
Cable and X-Force #1 from 2012 is a great issue for reintroducing the classic concept of the team after several years of exploring different directions. Cable brings back together many of his old comrades in this issue, written by Dennis Hopeless and drawn by Salvador Larroca. It's a great starting place for new readers and a place for fans of the series to get back on. Domino, Boom-Boom, and other familiar characters come back into the fold in a story that puts the team back into its somewhat antagonistic role from the '90s by pitting them against the Uncanny Avengers over a mission gone wrong.
X-Force #116
Just as the New Mutants team evolved into X-Force, X-Force would evolve again into X-Statix. Issue #116 of the series is key for a number of reasons, including the introduction of one of the strangest and most unique X-Men characters, Doop. The tone and style of the series changed dramatically, moving away from the over-the-top action of the 90s and embodying the quirky style of artist Michael Allred.
Allred's art is outstanding in this issue, bringing to life a brand new cast including U-Go-Girl and others. Though the title of the series changed to X-Statix, it maintained its traditional X-Force numbering until the end of the series with issue #129, where it was then re-launched with a new #1 issue.
Uncanny X-Force #1
The tone of X-Force shifted again in Uncanny X-Force #1, written by Rick Remender and drawn by Jerome Opeña, to fantastic results. Remender reimagines X-Force as a black ops team that goes after threats to mutants before they can manifest in many cases, taking the concept further into the realm of the "Dark X-Men." The issue puts some of the X-world's heaviest hitters, including team leader Wolverine, in the role many fans love to see them in, taking down major threats and wrestling with ethical issues like whether or not to kill a child version of Apocalypse.
Uncanny X-Force #18
The darkness inherent in Uncanny X-Force and in its characters is perhaps best realized in issue #18 of the series, the final chapter of "The Dark Angel Saga." Warren Worthington has fallen back to his Archangel persona and is forced to face off against his teammates to protect the Four Horsemen of the Apocalypse, including Pestilence, who is carrying his child. The issue is deeply tragic, featuring a sequence where Psylocke creates a mental oasis where she and Warren live out a peaceful life as he dies from wounds sustained in the battle.