X-Men #102 is a cool book as it features the first battle between Colossus and Juggernaut - check out its awesome cover.  It includes the origin of Storm. Black Tom Cassidy appears.  It also happens to be the 2nd appearance of Phoenix (which is not yet widely appreciated)!  Chris Claremont story and Dave Cockrum art.  This book is graded 9.4 NM with white pages by CGC.