Unobtainium and Expensivium are very vital, curious, yet annoying elements. They are commonly used in parts for electronic devices, particularly those in the world of broadcast RF transmission.
Although no link between actual physical toxicity to humans or any other animals has been proven with Unobtanium or Expensivium, those involved in occupations where they have to procure and work with Unobtanium and/or Expensivium parts tend to suffer a greater number of headaches.