Sophia Bush

Actress, Humanitarian & Author

Ian Somerhalder

Actor Known for "The Vampire Diaries;" Animal & Environmental Advocate; Founder of The Ian Somerhalder Foundation

Jenna Marbles

YouTube Sensation

Melissa Rivers

Actress, Television Host & Producer, Equestrienne, and Philanthropist; Daughter of Late Comedian Joan Rivers

Tim Gunn

Fashion Icon, Former Co-Host & Mentor of "Project Runway"

Bill Richardson

Former Governor of New Mexico; Former U.S. Energy Secretary

Bill Richardson On Nuclear Threat Diffusion (HBO)