Benjamin Parker is the uncle of Peter Parker, aka Spider-Man. Throughout every Marvel Comics continuity, he has been a kind and sagely figure toward Peter and his tragic death is what spurs Peter to become a crime-fighter. He is gunned down by a criminal that Spider-Man had the opportunity to stop, but chose not to, thinking it wasn't his responsibility. It was only after Ben's murder that Peter came to realise the truth of his uncle's last lesson to him, "With great power comes great responsibility."
In most Spider-Man continuities, Ben Parker is gunned down whilst trying to protect his wife May and their home from a burglar. In the 2002 Spider-Man movie, Ben (portrayed by Cliff Robertson) is waiting in his car outside the library for Peter to return from 'studying' (though Peter was in fact participating in an amateur wrestling match) when the thug arrives and tries to take his car. Uncle Ben is shot and left in the street, surrounded by a crowd when Peter returns. He then dies in Peter's arms.
In the 2012 film The Amazing Spider-Man, Uncle Ben (this time portrayed by Martin Sheen) dies much the same way as in other Spider-Man continuities, only this time he is attacked while walking down the street at night looking for Peter following a fight between the two.