Although it's a number one poem for sterile academics to provide simplistic examples of Freudianism in a poem, Frost's "Stopping by Woods..." to me contains the two most haunting lines ever in a poem. Those last two lines still freak me out since the first time I read this poem.

Whose woods are these I think I know
His house is in the village, though;
He will not see me stopping here
To watch his woods fill up with snow

My little horse must think it queer
To stop without a farmhouse near
Between the woods and frozen lake
The darkest evening of the year.

He gives his harness bells a shake
To ask if there is some mistake
The only other sound's the sweep
Of easy wind and downy flake.

The woods are lovely, dark and deep,
But I have promises to keep,
And miles to go before I sleep,
And miles to go before I sleep.