Gonna list them all separately, because I do what I want!
Novel - The Hitchhiker's Guide to the Galaxy. Time travel isn't a HUGE deal in these books, but it happens frequently enough to count, and I simply can't ignore the greatest piece of sci-fi comedy ever written.
TV Series - Steins;Gate. Not only is the idea behind its time travel weird and interesting, but I love how the characters use it for really dumb, mundane things. It also helps that I love the characters in question, and that the story takes a really dark turn halfway through.
Movie - The Girl Who Leapt Through Time. Another example of a character using time travel for silly, petty things, only to have the story take a darker direction 40 minutes in. I love pretty much everything about this movie, and I feel it really nails the "consequences of time travel" plot perfectly.
Video Game - Chrono Trigger. It's as simple as time-travel stories get: Your friend invents time travel, shenanigans ensue, you learn some monster destroys the world in the future, and so you must stop him. The end. This game is perfect in almost every respect--appealing graphics, legendary soundtrack, likable characters, gripping yet simple plot, fun turn-based RPG combat, and multiple (some very funny) endings!