Fathers can be a terribly bothersome bunch. If you're the hero of an epic tale, half the time they turn out to be your worst enemy. If you're not such a hero, then maybe your father found his own way of pissing you off. Maybe he's set you up to marry the guy you hate, or he plans to hand over his title and fortune to his favorite general rather than you, his eldest son. Even if the title and fortune are intended for you, they're still not yours until the old fart is dead. Maybe he's got the woman you want (whether she's your real mother or not) or maybe he just doesn't appreciate the way you've been ogling your sister. Maybe your father genetically engineered you to be a Super Soldier or to power his super weapon and doesn't understand that you are so much more. Maybe you didn't even know it was him and he just got in your way. Maybe it was prophesied and You Can't Fight Fate. Maybe he beats you. Or your mom. Maybe all of these. In any case, your old man made a big mistake when he didn't off the offspring because his days are numbered. Daddy's goin down.
Patricide, the act of killing one's father, is one of the most serious crimes throughout history (it being one of the other things Oedipus is famous for). Such a taboo is therefore bound to be found in media. Often there is a degree of My God, What Have I Done? after the deed, reflecting exactly how horrible the crime is considered.
On the other hand, if you're not so very heroic, offing your dad may simply be the next big step in your long and promising political career. It could get you the woman of your dreams. And, lets face it, when you are the hero and your father is still alive, unless he's about to get kidnapped or murdered by the bad guy, then he probably is a horrible villain who deserves to die.
The killing of a parent is certainly very affecting and tells us a great deal about any character who would do it (And equally as much about characters who refuse to do it). When you're looking for some way of characterizing a hero as dark or causing him grieve heavily, this is always a good trope. What could be considered odd, however, is how often patricide is portrayed in fiction as opposed to matricide. As a matter of fact, try searching for a Matricide trope. You won't find it. This is probably a combination of Oedipus Complex and Most Writers Are Male.
Compare with Self-Made Orphan, when both parents are killed or otherwise done away with (usually Played For Horror whereas Patricide is Played for Drama), Archnemesis Dad, Evil Prince and Oedipus Complex. Contrast You Killed My Father. The more violent examples of Calling the Old Man Out may well involve this. May well be the life's goal of an Antagonistic Offspring.
- Berserk: The Kushan Emperor Ganishka is revealed to have killed his father (after having killed his little brother, favored by their mother). He ends up poisoned by his own son years later, and would have died had he not triggered his Behelit, transforming him into an Apostle.
- Guts kills his own father (figure) Gambino at a young age, when Gambino got drunk one night and went into his tent to try to murder him. He blamed Guts for the death of his lover Sys (Guts' foster mother) from the plague. There was considerably less angst after that, especially since Gambino admitted that he was the one who sold Guts to his rapist Donovan for three silver coins.
- In Madlax, Margaret Burton killed her own father Richard in very tragic circumstances. (He had been driven insane via the local Brown Note, she did it on self-defense). She blocked out the memories so well, they created a Literal Split Personality: the titular Madlax. (Or better said, two: the third one is the local Creepy Child, Laetitia).
- Tsubasa from Kannazuki no Miko Killed his Abusive Father in order to protect himself and and his brother Souma.
- Suzaku Kururugi from Code Geass fell into despair and killed his father, who happened to be Japan's First Minister, in order to make the Japanese troops surrender and stop the bloodbath caused with their (losing) war against Britannia.
- Lelouch has "kill Father" at the top of his to-do list for much of the series, partly out of revenge for some pretty severe Parental Abandonment, partly because he's the head of the evil empire that Lelouch despises. He eventually succeeds near the end of the series, and decides to kill his mother too while he's at it.
- In the 2003 anime version of Fullmetal Alchemist, this is Envy's life's goal. He's also got a Cain and Abel thing going on with his half-brothers.
- In the original Mobile Suit Gundam Evil Prince Gihren Zabi murders his father, Sovereign Degwin Sodo Zabi in order to graduate from Dragon-in-Chief to Big Bad. Note that for Gihren this is not a particularly shocking move. Neither is the fact that he uses a Wave Motion Gun to do it. And then his sister Kycilia confronts him and shoots him, invoking the trope as her reason to do so; Gihren would've been executed for patricide anyway, according to her.
- The Batman villain Hush killed his father as a child by cutting the brakes.
- One of the more unstable bad guys in The Punisher was shown to have a happy flashback in which he shot his mother, his younger sister and finally his father, as part of a power grab by his aunt.
- Thorgal: Thorgal is cursed by the gods for (unknowingly) killing his own father.
- Emperor Commodus from Gladiator murdered his father, Emperor Marcus Aurelius, in order to become emperor himself.
- In one Judge Dee story, the murderer was the victim's son, who had been having an affair with one of his father's wives. The judge verbally destroys the guy (Chinese society at the time placing a very great deal of importance on ancestor worship), who ends up Driven to Suicide.
- At the end of the first book of The Stormlight Archive, it's revealed that Shallan was somehow responsible for her father's death (though he probably deserved it).
- The Brothers Karamazov, in which the sons are accused/believe themselves guilty of their father's murder.
- In The Worst Crime In The World Father Brown solves one of these.
- According to legend, King Arthur was mortally wounded by his illegitimate son.
- In the Harry Potter series, both Voldemort and Barty Crouch, Jr. killed their respective fathers.
- In Warrior Cats, Brokenstar killed his father in order to become leader - as deputy, he was Raggedstar's successor.
- In Death: Immortal In Death reveals that Eve Dallas killed her own father when she was 8 years old. She had been suppressing memories of that time for years. As the series goes on, it is revealed piece by piece that her father Richard Troy was a Complete Monster who raped her and abused her for years, and that he intended to make her into a prostitute and sell her to child molesters. He caught her trying to feed herself and forced himself on her to punish her. Her arm got broken, she went crazy, and she managed to grab the knife she was using on the food. She killed him with the knife. If you do not feel sympathy for her over this, then you have no soul!
- In A Song of Ice and Fire Tyrion kills his father after years of psychological abuse and discovering that he had deceived him into thinking his wife and first love Tysha had been a prostitute.
- In the Seeker Bears book called Island Of Shadows, Nanulak the polar bear/grizzly bear hybrid uses Toklo mainly as a hitman in order to kill his polar bear father. Toklo backs off for two reasons: the first is that he was amazed to see the polar bear as Nanulak's dad, and the second was that he found out that Nanulak tricked him all along..
- Midsomer Murders: Though it's not shown onscreen, the episode in which the psychologist's middle-school kids are the murderers, they reveal at the end that the fall that killed their father wasn't accidental in the least.
- A Luthor family tradition on Smallville. Lionel Luthor killed his parents (which would include his father), and Lex killed Lionel.
- Morgana, on Merlin indirectly. She doesn't actually do the deed, but she enchants the amulet that does the deed and gives it to Agravaine to use.
- Regina, on Once Upon a Time. Sadly, she really did love him, which was why she killed him. She needed the heart of the one she loved most for the curse she wanted in order to fulfill her quest for vengeance.
- According to Buddhism, intentional murder of one's father is one of the Five Grave Offenses that will get you reborn into the lowest hell, Avici.
- Greek Mythology has Oedipus. He killed his father on the road outside Thebes, although some authors also make it an accident. In any case, he didn't know it was his father at the time, and had no hesitation about killing a stranger who got in his way.
- One of the major elements in the cosmogony of Warhammer 40,000 is that the Primarchs, genetically engineered Super Soldier sons of the God-Emperor, were stolen and later corrupted by Chaos. His favored son Horus fell the hardest, and eventually led the rebellion against him, until they faced off in a duel. Though he (Horus) died in the attempt, the Emperor was essentially turned into a barely more than a corpse, hooked up to an enormous machine that allows his body to continue living while his spirit continues to guide humanity (literally, in the case of the Navigators).
- The Playbody of the Western World begins with Christopher Mahon on the run after killing his father in an argument.
- Played with in Little Shop of Horrors: Seymour kills Mushnik shortly after being adopted.
- Under the Lich King's influence, Arthas Menethil kills his father for the crown of Lordaeron after being turned into a Death Knight in Warcraft 3. A mook even calls him out on it, demanding to know "How could you murder your own father?"
- God of War: Like in several Greek myths examples, Zeus hears a prophecy that his son Kratos would try to kill him and usurp his throne. This prompts Zeus to kill Kratos and send him to Hades, in turn prompting Kratos to escape and kill Zeus.
- Soul Edge/Soul Blade: A young Siegfried Schtauffen and his band of rogues attack a group of knights that they believe to be deserting the army. Unbeknownst to them, the group in question was simply returning home after their victory. Siegfried engages in battle with the leader of this group and beheads him; holding up the head in the moonlight reveals the identity of his prey: his own father Frederick. The realization pretty much shatters his mind, forcing Siegfried to go into denial, believing that someone else killed his father. He decides to search for Soul Edge in order to defeat this man, and the rest is history.
- Near the end of Exit Fate, Daniel kills his own father, Emperor Siegfried, who tried to determine his life via demonicpossession.
- In Metal Gear 2: Solid Snake, the titular character kills his father Big Boss when he goes rogue. Snake is later called out on this in Metal Gear Solid by his support-worker Naiomi
- In V3 of Survival of the Fittest before he's put on the island, Liam Black killed his father by cutting the brakes of the family car and causing it to crash. He got away with it scot-free.
- Averted in The Lion King: Simba thinks he (accidentally) killed his father, until it's revealed (to him) that his uncle Scar did it.
- Romans considered patricide to be the ultimate Moral Event Horizon. From The Other Wiki: "Ancient Rome had a unique punishment for patricide. The felon was severely scourged then sewn into a stout leather bag with a dog, a snake, a rooster, and a monkey, and the bag was thrown into the river Tiber. Plutarch records that the old laws of Romulus had no penalty for patricide because it was considered a crime too evil ever to be committed."
- According to Herodotus, the Persians believed that no man since the beginning of time had ever killed his own father, and that whenever this appeared to happen, it was evidence that the patricidal child was actually an impostor or changeling.