When asked to memorize a poem for a class ('twas an acting class in my case), I used the opening sonnet from Romeo and Juliet. The italics are where I stopped typing from memory and had to go check the poem in print:
Two households, both alike in dignity,
In fair Verona where we lay our scene
From ancient grudge break to new mutiny,
Where civil blood makes civil hands unclean.
From forth the fatal loins of these two foes
A pair of star-cross'd lovers take their life;
Whose piteous, misadventure'd overthrows
Doth, with their death, end their parents' strife.
The fearful passage of their death-mark'd love,
And the continuance of their parents' rage,
Which, but their children's end, not could remove,
Is now the two hours traffic of our stage;
The whic if you with patient ears attend,
What here shall miss, our toil shall strive to mend.