I think one of my first exposures to the concept of time travel was the Illustrated Classic edition of Twain's
A Connecticut Yankee in King Arthur's Court, which holds a special place in my heart. And I'd throw these along side it: Bradbury's
"A Sound of Thunder" short story, and all of Julian May's
Pliocene Exile/Intervention/Galactic Milieu series.
In regards to films, I'd echo the
PRIMER,
TWELVE MONKEYS and
BACK TO THE FUTURE mentions, and also toss out:
ARMY OF DARKNESS,
TIME COP and the original
PLANET OF THE APES. Though I think I believed that you could go backwards in time if you could just get the planet spinning the opposite direction.

In Television, it doesn't get any better than
QUANTUM LEAP and
LOST, IMO.

In comics, besides all the X-Men
"Days of Future Past" stories, follow-ups, revisions and regurgitation, I guess I enjoyed Walt Simonson's
FANTASTIC FOUR runs that featured a futuristic crisis that was threatening the present, the TVA, and Reed vs Doom battle across time! Also a fan of the
LEGION OF SUPER-HEROES time traveling stories. And yeah,
AVENGERS FOREVER was a great read.
And in gaming,
CHRONO TRIGGER and
THE LEGEND OF ZELDA: OCARINA OF TIME are time-shifting classics, but none compare to
MANIAC MANSION: DAY OF THE TENTACLE for sheer time travel tomfoolery and awesomeness.
