John Steinbeck's Of Mice and Men, hands down. To ban a work that so touchingly drives home the lesson of human compassion for "using offensive language and being unsuited to age group" has always set my spine a-bristlin'.

Huckleberry Finn and To Kill A Mockingbird are right up there with it.

Irony?...showing up on some banned books lists of late has been none other than Ray Bradbury's Fahrenheit 451...about burning books!