Well I eat fish 4-5 times a week (see location). The first step you will need to take is ask if it is fresh or frozen. ALL frozen fish has a more fishy taste than fresh. End of discussion. Eating frozen fish is borderline disgusting IMO. Now once you get to fresh fish. Saltwater fish tend to be less fishy then freshwater.
I personally HATE fishy tasting fish. My favorites are Tuna (raw or rare only), Mahi-Mahi, and Tilapia.
The absolute least fishy/metallic tasting fish though is Wahoo. My major problem with it is it barely has any taste at all, so make sure you get a sauce or something on it if eating it.
That's my Caribbean point of view. Shark and Swordfish are fine but have more metallic than fishy. I have no experience with halibut or orange roughy but have heard that they are less fishy tasting... I just don't get those here.
Finally, if you don't take anything else, take this. FROZEN FISH HAS MORE FISHY TASTE THAN FRESH. If it isn't fresh, don't eat it.