The most delicious surprise I've ever encountered in a sushi restaurant was at Fujiyama's in Prescott, AZ, when the waitress suggested to us (we were regulars there) that we try the hamachi (yellowtail) cheek. It was the most awesome cooked fish I've had in my entire life.
Someone suggested it to me years ago, I almost forgot about it.
I need to take a road trip (any excuse to get out of the summer heat soon!).