When buying sashimi, the tuna, the salmon and the mackerel are raw. There are occasionally other types of fish which are also raw, but things like prawns or octopus are always cooked. I avoid the salmon, personally, as it's always farmed.
*I highly recommend raw swordfish or raw shark. They taste great - they're not available in sashimi restaurants, though, so you'll have to visit the local fishmongers' for those, I'm afraid, and prepare them yourself.