Meerschaum?

[rharris]

pros; Meerschaum is light, it can be carved into great shapes. It tends to not "ghost" as briar can. It is easy to clean, as it usually just needs a pipe cleaner run down the stem.
cons; it is somewhat brittle and can break if handled roughly. Some people do not like the coloration as it absorbs tars and the like. As with most things it is a highly subjective personal preference thing. I happen to like them, and use a few of them.
Rich