What would you say the nastiest thing you've ever imbibed/eaten?

Probably chicken feet or possibly sheeps brain. The chicken feet were deep fried in batter and while the batter was nice, the legs themselves were a little too chewy for my liking. The sheep's brain is hard to describe, but it's gooey, the flavour wasn't too my liking and the thoughts that what I was eating were brains is also a bit of a turn off. Both were dares.

What is the most unusual thing you've ever imbibed/eaten?

Who knows? Witchetty grubs, croc meat, roo meat, escargot, baby calamari...
And all the ones I listed above were damned tasty (in a good way), I'd really recommend the croc meat.

I've found it's always good to keep an open mind, and most foods go great with cheese.