Aping his wall-crawling contemporary, Spider-Man, the Fantastic Four's own Benjamin J. Grimm enjoyed a long run in his very own team-up title, Marvel Two-In-One, beginning in January 1974. The series lasted for 100 issues and ended in June 1983, but astute fans may recall that the Thing's team-up concept actually got an earlier try-out in the final two issues of Marvel Feature (1st series), pitting the erstwhile Thing against the Incredible Hulk in issue #11 and then pairing him up with the Invincible Iron Man in issue #12; both illustrated by Jim Starlin.
Additionally, Marvel Two-In-One fielded seven annuals during its run; Annual #2 featured the 2nd part of the "Death of Warlock" which had begun in that years (1977) Avengers Annual and which also included the Thing's fellow "Team-Up" star, Spider-Man. Marvel Two-In-One featured pairings with most of the major Marvel Heroes of the period, although the latter issues tend to include second or even third-tier guests, and the series also memorably teamed the Thing up with an other-dimensional version of himself on two separate occasions, issues #50 & 100 (the last issue).
Despite its extended run, Marvel Two-In-One was never as successful as its sister title, Marvel Team-Up, but after the series was cancelled the Thing eventually managed to earn his own self-titled series in the wake of the first Marvel Super Heroes Secret Wars crossover.
Thing illustration by Anthony Castrillo.