Either something you've tried, or something you've heard of but would quite frankly rather starve to death than ever eat.
I'll start with three...
Casu marzu cheese, which contains live maggots [en.wikipedia.org]
Canned whole chicken [oddee.com]
Canned pork brains in milk gravy (check out the cholesterol level on what must be the least kosher food ever invented) [static.neatorama.com]