The Avengers and The Legion of Super-Heroes (And More!)
I am a huge fan of the 100-Page Giants that DC used to put out in the 70's.  It was cool to see an issue jam packed with multiple stories featuring Superman or The Flash from various eras,  The issues I really loved, though, were the ones that offered a wide variety of characters.  Detective Comics would feature a new Batman story with a classic tale of the Caped Crusader, but then there would be stories featuring characters like The Spectre, Hawkman, The Golden Age Green Lantern, Kid Eternity. Elongated Man and more.  Each issue was like a mini tour of the DC universe.