Ocellaris Clownfish (Amphiprion ocellaris)

The fish that made an entire generation want a saltwater tank, and honestly, it's earned the reputation. Ocellaris Clownfish are about as forgiving as saltwater fish get — tank-bred for generations now, disease-resistant, and completely unbothered by the fact that they're immune to their own host anemone's sting thanks to a mucus coating your fish would probably brag about if it could talk. They'll pair up, they'll host in anemones or just about anything else that resembles one (a powerhead, a piece of rockwork, your patience), and they'll outlive plenty of the "easier" fish people buy instead. Reef safe, peaceful with everything except their own kind in too small a tank, and about as close to a sure thing as this hobby offers.