How about so nasty and disgusting you couldn't even finish trying to clean it, butcher it up, etc...
When I tried my hand at waterfowling, I remember blasting a merganser with my Remington 870 (yes, it was legal...

) from a buddy's duckblind. As a gag, the two guys I was with told me that I have to clean it and take the breast meat to make soup with.
I was a "newbie" to duck hunting, but at least I knew that mergansers are a diving species and probably not that edible. Boy was I right... I took that merganser and cut open the breast and almost passed out from the stench!

And the hilarious thing is I "accidently" got back at the guys, because the stench was so bad, it stunk up the whole kitchen of the hunting cabin!