Gunn is the latest prominent celebrity to speak out in support of behalf of gay young teens following the suicide last week of 19 year-old student Tyler Clementi, whose encounter with a gay man was secretly filmed by a roommate and distributed on the Internet.
Popular "Glee" actor Chris Colfer, 20, who plays a version of himself as a gay high school student, has also joined the campaign by the Trevor Project -- a nationwide suicide prevention hotline for gay, lesbian, bisexual and transgender youth and those questioning their sexual orientation.
"How I Met Your Mother" star Neil Patrick Harris, and "Harry Potter" actor Daniel Radcliffe have filmed videos for the campaign in the past few days, along with U.S. talk show host Ellen DeGeneres.
In an emotional message on her talk show last week, DeGeneres said she was devastated at the news that Clementi had jumped off a bridge in New Jersey, and called for an end to teenage bullying.
"Things will get easier, people's minds will change, and you should be alive to see it," said DeGeneres, one of Hollywood's most prominent lesbians.