There are 2 things you can do:
1. Change the site name under Admin > General. However, this will change it for the entire site which you may or may not want. By which I mean, your long string "COD Questions and Answers for Black Ops and MW3" will appear at the end of every page title on the site.
2. Use an advanced theme (see docs). Override the head_title function with something like this:
if ( $this->template == 'qa' )
$this->content['title'] = 'COD Questions and Answers for Black Ops and MW3';
Hope that helps!