Some more mass grave jokes.

Some polite places for a mass grave:

helping to complete a quorum,
raked in with the autumn leaves,
separated from the plastics and the aluminums.

Some puckish places for a mass grave:

inside a spring-loaded can of peanuts,
balanced atop a door that's been left slightly ajar for the next person who walks in,
up the rectum of a man who's expecting a gerbil.

Some upsetting places for a mass grave:

in your soup,
hogging the only restroom in a Mexican restaurant,
not at the movies (even though they said they'd meet you).