I might have gone with Abel the Patriarch, but for two things. First, I don't think he quite qualifies as a Patriarch if his line died with him; second, he's not truly a martyr. Nothing against him, but really, martyrdom ought to be a choice, and Abel was in fact just a victim. He didn't refuse to accede to some demand by Cain; he just forgot to duck, as Tripp said of Thomas in Glory.
Basil the Great and Gregory of Nazianzus (Gregory the Theologian) were best friends who, with John Chrysostom, are credited with shaping the Orthodox Church. Basil and Gregory share a feast on January 2 in the Western Calendar, which is nice because they had a falling out for a while but then reunited. Oddly, early in their lives, they studied with Flavius Claudius Julianus, who would later become Julian the Apostate, the Roman emperor who would try to bring back paganism. But they weathered him, just as they weathered the Arian emperor Valens, who tried to take it to the Orthodox. [At the time, of course, they weren't known as Orthodox; they were probably called Consubstantiationists or something, but having won the heresy wars, they got to be Orthodox.] Greg and Basil were side by side against the Arians until Basil, then serving as Bishop of Caesarea, got Greg appointed bishop of Sasima. They had both been brilliant theologians and eloquent debaters, but while Basil was also a skilled administrator, Greg was a more monastic, contemplative kind of guy. Moreover, Caesarea was a nice posting, but Sasima was just a jerkwater town without much water. Greg didn't put a lot into it, and promptly ditched it when his dad fell ill and needed help running the episcopacy back home in Nazianzus. Basil showed up to remind Greg of his obligations, but Greg replied that those obligations did not include being his friend's pawn in a political struggle. Greg stayed behind to run things in Nazianzus, even though he declined the bishop's title when his father died.
One can look at their defense of the Trinity and the Nicene Creed as their most significant contribution. One might say that their development of the Rule as the governing principle of monasticism, later brought west by Benedict, was their magnum opus. I prefer the lesson in friendship, competing obligations, and forgiveness that they provide.