Wahad gave me Hollandse nieuwe when I visited the Netherlands. It's raw herring that's been gutted and de-boned, and kept on ice. To make it more appetizing, they put raw onions on it. You grab the tail, and drop it into your mouth, biting off everything in one go (at least, he did, so I did likewise). Holy. Christ.
I had never wanted to throw up from eating something before that, and I choked it down, but dear lord. I tried it, like you say, just to say I had, but damn damn damn. I won't forget that experience, or Wahad's bursting into laughter at my expression. It was worth it.