What an odd thing. Okay... let me see... Well I don't know about favourite, but there are titles that I think are beautiful, clever or just plain memorable. David Niven's autobiography for example, The Moon's a Balloon. What a great title!! :)
Other titles that stick out in my mind are quite the mishmash of genres. :) There's Beau Geste by P.C. Wren which just sounds beautiful and is such a clever play on words once you know the story. There is, of course, Harper Lee's To Kill a Mockingbird. Mary Stewart had some lovely, evocative titles for her mysteries, such as Thunder on the Right and Nine Coaches Waiting. Another that always pops into my mind is Still Glides the Stream by D.E. Stevenson, a British romance author. And I cannot finish without noting the GREAT titles of the Travis McGee mysteries. Written by John D. MacDonald, they are all based on colour - A Purple Place for Dying, A Tan and Sandy Silence, The Lonely Silver Rain, Pale Gray for Guilt. So many super titles!!