I'd submit assignment to a Shtrafbat. It was pretty much a death sentence, while still technically a "job". Assignment to a Strafbatatalion was the German equivalent, and similarly dangerous.

Other jobs that could be considered to have a short life expectancy would be front-line infantryman. Regardless of the country, you could expect to suffer the lion's share of casualties. Combat engineers, forward observers, tankers, pilots/crewmen, and other front-line assignments were also dangerous, although dependent upon the assignment perhaps not quite as deadly as being an infantryman. Some assignments in the Japanese Navy are also worth investigating (I believe their shipping fleet was hit particularly hard, and obviously Kamikaze planes, manned torpedoes, and the German Leonidas squadron also had low to no expectations of survival).