Effective when used by a class with high health but low damage (Such as a protection Paladin, or defense-specced Warriors) facing a class with low health but high damage (Such as a Rogue, or Mage).
An excellent 'If I'm going down...' resort.
An upgraded version is Super Sapper Charge.
Patch changes
Patch 1.6.0 (12-Jul-2005): The Goblin Sapper Charge can now be used while moving.