While in St Petersburg earlier this month, I ate:
Caviar sushi!
It was very, very salty. The yellow one was harsher in taste than the black and also slightly sour in taste. The black, still intensely salty but smoother somehow. Adding soy to this would have been plain wrong. The wasabi mixed rather oddly with the textures, yet still complemented the fishy taste.
It was good, really good.