I've read a lot of classics and I've enjoyed most of them but I'll try to enumerate the best - the must-read ones (the order is random, I can't choose between them, they're all great and unique):
* Wuthering Heights by Emily Bronte (a great book, one of my favourites)-the author is extremely innovative (for the 1850s)–you’ll definitely love it
* Jane Eyre by Charlotte Bronte
* Pride and Prejudice by Jane Austen (not as good as the Bronte sisters' but still a great classic) – if you like Austen you may also consider Sense and Sensibility, Mansfield Park or Emma
* Les Miserables by Victor Hugo
* The Great Expectations by Charles Dickens
* Robinson Crusoe by Daniel Defoe
* Gulliver's Travels by Jonathan Swift
* The Picture of Dorian Gray by Oscar Wilde
* War and Peace and Anna Karenina by Leo Tolstoy
* The Idiot by Fyodor M. Dostoyevsky
* Le rouge and le noir (The red and the black) by Stendhal
* All Shakespeare’s works (As You Like It, Macbeth, Hamlet and so on)
* Vanity Fair by William Makepeace Thackeray
* Gone with the Wind by Margaret Mitchell
* The Great Gatsby by F. Scott Fitzgerald
* To Kill a Mockingbird by Harper Lee (don't know if it's already a classic but...you get my point)
There are many more but these are the most known and most widely considered CLASSICS. They're all must-read books – my opinion is that you can’t read the contemporaries properly if you haven’t read at least the most important ‘classics’ of the ‘canonical’ authors.