As any liturgically-minded Catholic is well aware, the Church doesn't have room on her calender for all of her canonized saints. (It's hard to squeeze several thousand saints into 365 days!) Those who do make it onto the universal calender--that is, those saints whose feast is "mandatory" for everybody everywhere--are there for at least one of two reasons. Either their life and writings are of some theological significance, or they are the object of great popular devotion.
While there is a degree of overlap, in practice it's usually fairly easy to tell in which category a particular saint falls. For example, St. Padre Pio is not a Doctor of the Church, and I have yet to see a St. Cyril of Alexandria medal.
St. Athanasius is obviously one of the "theological" saints, but at the same time he is one of the saints who is very near and dear to my own heart! Not only did he help save the Church from the rampant heresy of Arianism while helping to define our Christology, but he did so with a level of virtue that I find personally very inspiring.
St. Athanasius was born in A.D. 295 and died in 373. As a child, he would have seen the last of the major persecutions against Christians. A a young cleric he accompanied the bishop of Alexandria to the first Nicene Council. This is the ecumenical council which gave us the Creed ("...I believe in Jesus Christ, the only son of God, eternally begotten of the Father, God from God, Light from Light, true God from true God; begotten, not made, one in being with the Father...") which refutes the Arian tenet that Christ was a created being and therefor less than God. St. Athanasius himself later became the bishop of Alexandria, despite the protests that he was to young (he is believed to have been twenty-eight at the time, while the canonical age was thirty).
Although the first Nicene Council formally condemned Arianism, there was a major Arian revival during St. Athanasius' episcopacy. He fought against this heresy with remarkable courage, risking his life and suffering exile several times. He stood his ground, even though it often seemed that he was fighting a losing battle. I'm not sure how accurate this statistic is, but I have heard that at the time seventy-five percent of the Church's bishops were Arian. (And we think we have it bad!) This is what gave rise to the expression: Athanasius contra mundum, or "Athanasius against the world."
I'm sure a lot of my friends place my devotion to St. Athanasius under the same heading as my Canon law hobby--that is, as one of my weird, hyper-intellectual idiosyncrasies. Still, I think that it would be good for us in this day in age if personal devotion to St. Athansius became more widespread.
Today, we often hear people talk about how they believe that Jesus was a good man or a great moral teacher, but not God. This point of view, common as it is, really isn't too far off from Arianism! Certainly, St. Athanasius' prayers could help us here. And at a time in history when we are so beset by relativism, I think it would do us well to meditate upon that life of a saint who was willing to sacrifice everything (and offend a lot of people!) to defend what he knew to be the objective truth. Certainly, St. Athanasius' prayers could help us here, especially when we as Christians find ourselves called to be contra mundum.