Braum -- Some speculation and clarification
So obviously the new champion has been teased with this cute but also awesome little video. I saw a few people around here (who I won't name) seemingly outraged that the next champion was a "poro champion". Guys...it's a manly shield guy. Quite the opposite.
We know from a recent quote from a Rioter (Zenon? Some designer I believe) that the next champion is meant to be a support. He is shown clearly defending someone in need, showing him to be a compassionate fellow and also possibly showing off an aspect of his mechanics. We know he has a shield, which is rather useful for a support. Since it's the only thing he uses in the video, we can probably assume that he is defined primarily by his shield and not any other sort of weapon (also evidenced when he reaches down with his other, empty hand.) We also see him give the poro a mustache and laugh and joke with him--evidence that he is a jovial, happy fellow. He's also shirtless and has a huge mustache himself, furthering his theme into the realm of "man support" which is a niche that isn't yet filled, really. (Some could argue Taric or Thresh, but these guys are defined primarily by other things, and not by their machoness) We have plenty of compassionate, gentle female supports, why not a rowdy, rough jovial male support?
It remains to be seen if the little poro featured in the video is actually a part of his kit or not. I doubt they would take a champion like this and make his abilities primarily feature the poro--this does not seem like the champion to do that with. There is a possibility that the poro was just there to serve as a cute way to show off what this champion is all about. So enough about Riot "running out of ideas" or whatever the complaints have been. It's clear that they haven't (Vel'Koz is evidence enough of that).
TL;DR Braum--the recently teased champion--is a jovial manly shield support champion who just happens upon a poro in need.