Through out time, people have written stories about time travel. Like Dr. Who, Phineas Fog from "Voyagers!", Dr. Sam Beckett, Marty McFly, George (The Time Machine), Black Adder (watch the last season before trying to correct me), or my favorite, Merlin from Arthurian legend.
The Disney version does not cover the odd nature of Merlin's interactions with time (mostly covered in "The Once And Future King"). In particular, Merlin is traveling backwards through time. He is growing younger and he can see the future but can not remember the past. Merlin has an interesting take on morals, because of his condition he has no idea what good or bad things a person has done, only what they will do. So he could hate a saint because he knows they would kill someone 5 years down the road, or love a murder because they may save a baby tomorrow. I still think this is one of the most interesting uses of time travel in literature and brings up the philosophical debate of whether potential is more important than past or not.
So... What is your favorite example of time travel in a story (TV, movie, or written)?