Captain Jack Harkness
Jack is a time traveller and former conman from the 51st century. A bisexual.  In contrast to the wiser and older Doctor, Jack prefers a hands-on solution to the problem at hand. As a consequence of his death and being brought back in the last episode of the 2005 series of Doctor Who, the character becomes immortal, which does not change during both Doctor Who and Torchwood.