2. The Uncanny X-Men And The New Teen Titans
Comics historian Matthew K. Manning called the X-Men/Teen Titans crossover "one of the most well-received crossovers of its time - or of any time for that matter," and it's not hard to see why. Scripted by long-time Uncanny X-Men writer Chris Claremont and illustrated by legendary Thor artist Walt Simonson, the one-off book aimed to cash in on the extraordinary popularity of two of DC and Marvel's flagship team books and not only ended up succeeding with aplomb but also telling a thrilling tale of Darkseid resurrecting Dark Phoenix in an attempt to attain the unlimited power of "The Source". The two teams struggle against Darkseid and his forces, who count Deathstroke the Terminator among them, and successfully convince the newly-reborn to sacrifice herself (again) in order to foil the villains' plan and save the universe. Seeing the young heroes working together is a thrill, and Claremont is the master of inter-team conflict, so it's a shame that the planned sequel to the one-shot was abandoned in the fallout of the initial JLA/Avengers cancellation.