Probably my favourite Warhammer 40K model of all time.
The Grot Bomm Launcha, or Grot Bomb Launcher, is an Ork artillery vehicle which fires a large, guided missile that is piloted by a single Ork Gretchin. The Gretchin sacrifices himself in order to ensure that the missile successfully reaches its intended target.
It is unknown by Imperial savants whether this is a punishment forced upon the small Orkoid creature or if perhaps it is even some form of reward. It appears that the Gretchin controlling the missile does not fully understand where this course of action will take him, and it may be possible that these small creatures are simply misled by their Ork Mekboyz into undertaking this suicidal duty.