My favourite Marian prayer is the Memorare (Remember O Most Gracious Virgin Mary)
Remember, O most gracious Virgin Mary,
that never was it known that anyone who fled to your protection,
implored your help or sought your intercession,
was left unaided.
Inspired with this confidence,
I fly to you, O Virgin of virgins, my Mother;
to you do I come, before you I stand, sinful and sorrowful.
O Mother of the Word Incarnate,
despise not my petitions,
but in your mercy hear and answer me.