It must be said, I didn't agree with the suicide depiction in the Volkswagen advert episode. The VW advert was done differently, and not made to look to be serious. That said, such a depiction could still result in the accidental death of a child. In the case of this episode, Clarkson is shown to be picking up a handgun and loading the clip, then some footage was botched in of him pointing it at his head. Now, the fact that he was most likely handling a gun that wasn't loaded does not make it okay for him to be pointing it at his head. The way it was depicted, many will be fooled into thinking it was a loaded gun he was pointing at his head.
Loaded or not, pointing a gun at yourself is not okay. The depiction on a show watched by children, especially in what is a more serious setting than in the VW advert, is morally irresponsible.
http://gunnuts.net/2009/08/25/all-guns-are-loaded/
http://thefiringline.com/Misc/safetyrules.html