X-Men #98 (Marvel, 1976)

The "All-New/All-Different" X-Men had just taken over from the reprints of the original X-Men just four issues before. So this is a very early appearance for Storm, Nightcrawler, and Colossus. Although he pre-dated this class by just a few years, this is also a very early appearance of Wolverine, who did not even make the covers of Issues 94, 95, or 97! Combine that with definitive team member Cyclops and some quintessential bad guys, the Sentinels, and you get one fine action-packed cover!