On today's Oprah Winfrey Show—the last before next week's grand finale—the Queen of Daytime revealed her favorite guest of all time. Taking top honors was Dr. Tererai Trent, who broke free of poverty and abuse in her native Zimbabwe to achieve success. Trent's big dream has been to open a school for girls in her home village. And it was realized today when Winfrey surprised her on the air with a $1.5 million donation.