Under Armour and Nike are direct competitors in the sporting goods landscape, so it makes sense why both CEOs aren't exactly best friends. Under Armour CEO Kevin Plank established an annual routine of sending Nike CEO Phil Knight a Christmas greeting card that read, "You will know our name." According to Plank, who spoke with NBC, the gesture wasn't in an effort to be spiteful, but he says that it was a bi-product of ingraining an "us versus them" mentality into his company's culture. Kevin Plank