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Zippy the Pinhead, created by Bill Griffith, is probably the most surreal comic strip, if not ever, then certainly in publication today. It's notable for being one of very few strips that began and continue in college newspapers and alternative weeklies, but which is also syndicated to mainstream newspapers. The humor is obviously geared towards those who prefer something... outside the norm. I like it, and a lot of people seem to as well, as Zippy appears in quite a few newspapers. It's not for everyone, though.
This one is from fairly recently, but the basic premise and feel of the strip hasn't really changed much over the years. If you think, "This is just weird and dumb and makes no sense," and you feel yourself saying that in a negative tone of voice, then this comic is not for you. If you think that in a positive tone of voice, as I do, then you'll probably like it.