In his book The Culturally Savvy Christian, Dick Staub tried to draw out what exactly such a Christian should look like, and he frequently looked back to the Inklings, particularly C. S. Lewis and
J. R. R. Tolkien, as the model; these men certainly, clearly reflected the spirit of Christianity in their lives and works, but they also were influential in moving, and especially in Tolkien's case, forming culture.
So where have the "culturally savvy" Christians gone today?
Well, some people would probably say "Look at Bono".
The man hasn't ever shied away from claiming Christianity, his charitable work(co-founding the (RED) campaign, for example) is known of across the globe, his influence is pretty impressive (a perfect example), and no can say that U2 has not been a cultural influence. Really, it's kind of like Mark Wahlberg's character said in Shooter... everybody just likes Bono.
Here's an older, LONG article from Christianity today on the man, exploring his exploits on and off the stage. This article came back up because of the release of U23D, which CT also reviewed pretty positively.
So check out the articles. I'm a fan of Bono the man, myself, and whenever I get to listen to U2, I like them. Maybe I'll have to check out the movie. Maybes aside though, we all should consider, especially those who are going to all sorts of jobs in the secular world, i.e. most people, what it must look like for us to really be 'in the world but not of the world', citizens of the Kingdom of God who inhabit the world. This is the question that discipleship boils down to, and its answer is crucial for all the Body of Christ.