And now, for a curse that almost _nobody_ is going to get:

Spring of Drowned Wizard of Yendor:

Primary advantages:
  It could be impossible to die while in cursed form... ("Did you think that
thou couldst kill me, fool?")

Primary disadvantages:
  Any injury causes immediate, unavoidable teleportation to the nearest
staircase.
  The "double trouble" effect would be confusing to anyone who is _not_ the
true Wizard, and I'd rather not think about what'd happen when either one or
both of the Wizard gets splashed with hot water...

 -Andrew (who probably should've just kept his mouth shut...  Somehow I
think there aren't more than half a dozen people here who play NetHack,
anyway...)