Heroic Dolphin

It seems that in most media, especially most fiction, dolphins will be portrayed primarily as heroic and helpful creatures. They're a very marketable species of hero, partly because of their cuteness, but also partly because of real-life stories of dolphins saving human lives.

Of course, in real life that isn't the whole story; many dolphins are known to kill for fun, and it's plausible that some of these might even be the same dolphins; being willing to Pet the Dog doesn't rule out the possibility of kicking a different one, after all.

That said, Deconstructions of this are becoming increasingly popular, at least in non-fictional media.

See also Friendly Playful Dolphin, though dolphins can be portrayed as playful and friendly but not heroic, or heroic but neither playful nor friendly. Often overlaps with Sapient Cetaceans, though cetaceans can be dolphins or whales, and also, dolphins can be portrayed as sapient but not heroic, or heroic but not sapient.

Comics

 * The comics based on the Ecco the Dolphin game series make Ecco's noble nature clear in no uncertain terms; though his somewhat dark methods of fighting enemies may make him seem like a bit of an Anti Hero.
 * Porm, the dolphin who acted as a surrogate mother to Aquaman.
 * Ghost Rider was saved from a killer shark by dolphins.
 * In Grant Morrison's Animal Man, one story features Animal Man saving dolphins from murderous Scandinavian townsfolk who kill them for fun. At the end, one of the dolphins saves an evil townsperson from drowning.

Live Action TV

 * Flipper might be the Trope Codifier as far as recent western media go.
 * Darwin the (talking) Dolphin from Sea Quest DSV.
 * In Ninpuu Sentai Hurricaneger/Power Rangers Ninja Storm, the water-themed Blue Ranger has a dolphin motif and mecha.

Film

 * In "Jaws 3-D" Cindy and Sandy rescue Kay and Mike from a shark after attempting to keep them out of the Galleon.
 * Fa and Be from Day Of The Dolphin.
 * Both animated Titanic movies have them: the first has talking dolphins that are trying to stop evil whalers, and the second has dolphins who don't talk, but help save people from the sinking ship.

Literature

 * Venus Among the Fishes is about Coral and her brother Snapper who are sent on a journey to save their pod from orca attacks.
 * In Journey of the Dolphin King House Rinaldo the leader dolphin of a band of dolphins and his goal is to help his dolphin pod find a new home.
 * Dolphin's Dance is about a man reincarnated as a dolphin. One of the events in the story involves him saving a college student who was in a surfing accident.
 * The Tempests Roar is about a white dolphin named Apollo whose destiny is to save whalekind from destruction on this planet man calls Earth but whales know as Planet Ocean
 * In The Roman Mysteries book The Dolphins of Laurentum, a dolphin rescues Lupus after he nearly drowns from staying underwater too long while diving. It is also strongly implied that the same dolphin discouraged Lupus from deliberately leaving behind another diver who had been trapped by a giant octopus, though in fairness to Lupus he had a good reason for wanting the trapped person to die. The same scene is also in the Live Action TV adaptation. The book also references several examples of the use of dolphins in Classical Mythology, including stories of shipwrecked sailors being rescued by dolphins.
 * The cyber hacker dolphin from Johnny Mnemonic.
 * Dolphin Way Rise of the Guardians has a dolphin protagonist who must break his civilizations rules to save his friends.
 * Dolphins of Expedor is about Timothy Shore, a yellow, fourteen year old 'talking' dolphin, gets sucked into a whirlpool adventure to save his city 'Expedor' from certain destruction
 * Dolphin Journey has a dolphin protagonist and hero that goes out on a journey to create a song that will keep other dolphins from being trapped in nets.
 * Dinotopia - Dolphins were responsible for bringing all shipwreck survivors to the island.
 * In the first Age of Fire book, dolphins rescue a drowning baby dragon and help him to land. A few months later and considerably larger, the dragon sees fishing boats attempting to capture the dolphins...
 * In Native Tongue, Dickie the Dolphin isn't strictly friendly, (or perhaps overly so, ) making this perhaps a Double Subversion.

New Media

 * Cracked deconstructs this by listing dolphins in both The 6 Biggest Assholes In The Animal Kingdom and The 6 Cutest Animals That Can Still Destroy You.
 * Kip The Dolphin is a flash game that has a dolphin who is supposed to save as many deep sea divers as possible.

Tabletop Games

 * Some editions of Dungeons and Dragons have depicted dolphins as sentient Good-aligned creatures with their own patron goddess.
 * In one Traveller sourcebook a story is told of some uplifted sapient dolphins who helped bring to light a scandal involving the secret enslavement of an intelligent species by a megacorporation.
 * In Rifts' Underseas, P Cs can in fact choose to play as a Dolphin (or an Orca or even Humpback Whale).
 * The board game Escape from Atlantis (recently reprinted with the name Survive!) has dolphins which give swimmers a boast of 3 spaces per turn rather than the usual 1.

Video Games

 * Ecco the Dolphin: Humans aren't even present, at least not in the Genesis games, but Ecco saves not only his family, but the world as a whole, from being consumed by Vortex aliens. The other dolphins also bravely show up en masse to battle the Vortex at the end of the second game, and the Resistance dolphins from Defender show some courage in helping Ecco overthrow the Clan.
 * Played straight with the empathic, pacifist Liir race from Sword of the Stars...until you attack them, at which point they'll declare you Suul'Ka and never stop killing you until your entire race is just a fading memory. Liir soldiers are called "Black Swimmers" and are never permitted to interact with civilian Liir, lest their murderous tendencies corrupt the entire species.
 * As far as the planet-bound Liir are concerned, the Black Swimmers are all dead to them. They hold a funeral service for each Liir who signs up to join the fleet.
 * Mike rescues a dolphin in the second stage of Star Tropics..
 * Red Alert 3 is set to include dolphins with sonic weapons as seagoing infantry for the Allies, and the 3rd political party in the USA, the Federalists, adopted the Dolphin as their symbol. Of course, dolphins are already Allied sea units in Red Alert 2 as anti-giant squid weapons.
 * Super Mario World features a few levels with Scuba-wearing Dolphins that jump out of the water regularly and can be used as platforms to reach far away areas. They can be eaten by Yoshi too.

Web Comics

 * The Adventures of Dr. McNinja story Death Volley has the implication of dolphins getting revenge on Agent Bearclaw. His story: "One time I swam out to sea, and pretended to be injured so that dolphins would swim up to rescue me. I did this so that I could kill them with my bare hands."

Western Animation

 * Subverted in The Simpsons, when Bart, Homer, Flanders and his kids stranded at sea and being approached by dolphins. Flanders is relieved, stating that dolphins always help people lost at sea. The dolphins merely chitter that they are all going to die, giggle a bit, and then leave.
 * Later inverted in a Treehouse Of Horror episode when dolphins rebel aganst humans, take back the land for themselves, and force humans back into the sea.

Real Life

 * Brutally subverted in real life: Dolphins are the closest thing to an Always Chaotic Evil race in real life, it seems - they have some Pet the Dog moments, but sharks are less vicious than the little buggers.
 * They rape human women on occasion. Does anything really need to be said at that point?
 * AND human men.