What animal has the most disgusting defense mechanism?

Everyone knows that skunks can emit a rather unpleasant odor, but my favorite defense mechanism belongs to the sea cucumber, which uses its cloaca—a sort of multipurpose orifice/hole that serves as a mouth, anus, and anything else that needs a hole—to eject parts of its internal organs, including its intestines, various blood vessels, and small bits of gonad (sea cucumber internal private parts). In the process, the cloaca tears a little bit.

I can't speak for all sea creatures, but having someone's internal organs ejected into my face would probably surprise me. This is its attempt to surprise its attacker so it can escape.

I suggest Zefrank's True Facts About Sea Cucumbers on YouTube for a hilarious video on the subject.

I hope this is useful.

The bombardier beetle is often cited as having one of the most disgusting defense mechanisms. It can eject a hot, noxious chemical spray from its abdomen when threatened.