DC's The Brave and The Bold title paired up super-heroes for some fascinating tales, yielding plenty of key issues. Several of these fan favorite keys turn up here, with this 1963-1964 The Brave and The Bold comic lot of (3).
#50 with the first crossover appearance of the Martian Manhunter outside of Detective Comics, teamed with the Green Arrow (VG 4.0)
#51 with Aquaman and Hawkman team-up, predates Hawkman #1 (VG-FN 5.0)
#54 with Kid Flash, Aqualad and Robin, the first appearance of the Teen Titans (FN+ 6.5)