Crossover with Doctor Who/Torchwood
Jack Harkness, ex-time agent, ex-con man, ex-companion, current leader of the Torchwood institute. Jack Harkness, man of the 51st century stuck in the 21st, pledged to protect the earth from extraterrestrial and 'supernatural' threats. He fought every enemy imaginable, and some that defy imagination. Faced by his greatest opponent, he called upon the Doctor to save the human race... and ends up in Equestria.
Oh, did I mention he doesn't stay dead?