Rebar

During a fight with a nest of vampires in 15.20 Carry On, Dean sustains a fatal injury when he is impaled on a rebar.

Fans who were upset by Dean's death, and particularly that it was during a run-of-the-mill vampire fight and not an epic heroic battle, dubbed the rebar a "rusty nail". Some took it further, charging sarcastically that Dean had died from tetanus that he got from said rusty nail!

Others doubted the injury could kill Dean, however the rebar could've ruptured the descending part of his thoracic aorta, which runs along side the spine.