I agree with bel - it's probably more interesting to ask individuals for their recommendations but you asked for a list so here is one:

http://www.stanford.edu/~bkunde/best/bl-crank.htm#T

Assuming it's OK with the author I'll include the top twenty:

Rank Author Title Date
001 Fitzgerald, F. Scott; Great Gatsby, The; 1925
002 Orwell, George; Nineteen Eighty Four; 1949
003 Heller, Joseph; Catch 22; 1961
004 Steinbeck, John; Grapes of Wrath, The; 1939
005 Nabokov, Vladimir; Lolita; 1955
006 Joyce, James; Ulysses; 1922
007 Orwell, George; Animal Farm; 1954
008 Golding, William; Lord of the Flies; 1954
009 Salinger, J. D.; Catcher in the Rye, The; 1951
010 Vonnegut, Kurt, Jr.;Slaughterhouse Five; 1969
011 Huxley, Aldous; Brave New World; 1932
012 Ellison, Ralph; Invisible Man;1952
013 Faulkner, William; Sound and the Fury, The; 1929
014 Joyce, James;
Portrait of the Artist as a Young Man, A; 1916
015 Hemingway, Ernest; Sun Also Rises, The; 1926
016 Wright, Richard; Native Son; 1940
017 Kerouac, Jack; On the Road; 1957
018 Woolf, Virginia; To the Lighthouse; 1927
019 Lee, Harper; To Kill a Mockingbird; 1960
020 Walker, Alice; Color Purple, The; 1982

It is a composite list of four lists: Modern Library list, Library Journal list, Koen Book Distributors list, Radcliffe Publishing Course list - the webpage below analyses their strengths and weaknesses:
http://www.stanford.edu/~bkunde/best/bl-sourc.htm#T

I'm sure that there was a BBC programme with a list, so I'll keep looking.