And there's always Tom Lehrer's Oedipus Rex (When he saw what he had done/He poked his eyes out, one by one/A sorry ending for a loyal son who/Loved his mother). I see what you mean about Lehrer and Silverstein having a corner on the market, but I think my all time fave is Mrs. Ravoon, though, spookily enough, the title link seems to have vanished from DT, and I could only find it with a phrase out of the song.
You particularly don't want to sing this one, and these verses at a dinner party:

I stood by the water, so green and thick,
And I stirred at the scum with my old, withered stick,
When there rose from the depths of the limpid lagoon
The luminous body of Mrs. Ravoon.

I pulled in my line and I took my first look
At the half-eaten horror that hung from my hook.
I had dragged from the depths of that limpid lagoon
The bloated cadaver of Mrs. Ravoon.

Blessings,
Barbara