What makes this Tibetan Buddhist rosary, or mala, different from the Catholic & Islamic rosaries seen so far on this site? 

Well, it has more beads--108, to be exact--but if it's just more beads you want, you can always buy a bunch of other rosaries.  No, what makes these mala special is the source from which they're carved.

A human skull.

Like any number of spiritual movements throughout history, Tibetan Buddhism incorporates reminders of mortality in its rituals & beliefs.  Modern-day skull chic reflects a similar impulse, and lest certain folks think this is a sign of rampant paganism, it would be good to remember that Christianity itself has a long tradition of skull & bone devotion.  In fact, this site sells a Christian rosary carved from Tibetan skulls.

Ain't ecumenism grand?