The NPI-16 is a short measure of subclinical narcissism that has shown meaningful face, internal, discriminant, and predictive validity. It can serve as an alternative measure of narcissism when situations do not allow the use of longer inventories.

Reference:
Ames, Daniel R., Rose, Paul, and Anderson, Cameron P. (2006). The NPI-16 as a short measure of narcissism. Journal of Research in Personality, 40, 440-450.

Download the paper:
  Ames, Rose, and Anderson (2006)

Download the scale and scoring instructions:
  Word document
  PDF document

The NPI-16 draws its items from Raskin and Terry's NPI-40:

Raskin, R., & Terry, H. (1988). A principal-components analysis of the Narcissistic Personality Inventory and further evidence of its construct validity. Journal of Personality and Social Psychology, 54, 890–902.