The X-Men #128

This December 1979 issue of Uncanny X-Men promises chaos on a grand scale, with the tagline "The Day Reality Went Wild!" setting the tone perfectly. George Pérez and Terry Austin's cover is a wonderfully disorienting spectacle — buildings twist at impossible angles while the X-Men (including a red-optic-blasting Cyclops, an airborne Jean Grey, a steel-skinned Colossus, and several teammates tumbling through the mayhem) struggle against a reality that's literally come apart at the seams. Chris Claremont and John Byrne were firing on all cylinders during this era, and "The Action of the Tiger!" looks like exactly the kind of kinetic, anything-can-happen adventure that made this run so beloved.