In one of my favorite episodes, an air force pilot in the middle of a battle flies his biplane through a cloud only to be transported into the future. He lands at an airfield and begins a conversation with an old guy on the ground, where he figures out that the old guy is his best friend from the past. His friend, too old to see well enough to recognize who he's talking to, tells the pilot the story of how "Ol' Leadbottom" had saved his life and many others in a fierce battle before going down. The pilot jumps back in his plane and returns to the past, knowing that he will die but knowing what he must do.
Other favorites include Talking Tina, the all-powerful boy who could "send people to the cornfield," and the Hitchhiker, of course. "Going my way?"