The so called "white tuna" you can get at American sushi places. It's actually a fish called escolar or oil fish, and if eaten in great enough amounts it will give you the oil shits for days. It has a very rich flavor, a somewhat buttery taste. I've read a lot of other countries have banned it because of it's properties, but I don't think I've ever eaten more than the limit. One of these days I might overstep the boundary, but that is a risk I'm willing to take.