Alternate Realm Boon

Isekai fiction has the common trait of having the protagonist receiving a power, skill, or even a legendary item that gives them an overwhelming advantage over the inhabitant of the other world.

Common in most Eastern Portal Fantasy and Transmigration-type light novels, where it is a power(s) that can make a massive benefit or the go-to means for the protagonist to use, especially in combat. The settings of the other world take place in a world that has RPG features that come in the form of a skill. Others would have magic within the setting where the main character has a high affinity and even using the modern study of science in combination for higher effectiveness. For the case of items, they are usually legendary weapons that are known in the world to be wielded by the summoned hero in order to face a danger the inhabitants cannot without a chosen one brandishing it. Another fascinating example is characters who are reincarnated by a deity and are blessed with something that eases any difficulty in a new world. Another method is reincarnating into a high-class monster or a non-human being.

Western Portal Fantasy seems to use the trope within such stories rarely. They often would be placed in a fantasy setting where their modern education or even technology would give them an advantage.

Anime and Manga

 * In Arifureta: From Commonplace to World's Strongest, the students and their teacher got a job and magic when they transported to another world besides Hajime, who is the main protagonist. He gets stuck with the rare job of Synergist that is a non-combat one with the power of transmutation that can act as a craftsman or blacksmith.
 * The Rising of the Shield Hero has four people from a different world summoned with Four Legendary Weapons. The four Legendary Weapon comes in the form of a sword, spear, bow, and shield. The weapons grant their users different abilities while also having different forms under certain conditions or absorbing materials. The protagonist’s Legendary Shield gives him a high amount of defense but lacks offensive capabilities like the others.
 * Re:Monster has the main character Tomokui Kanata who was reincarnated into a goblin named Rou. He kept his memories and his Esper ability called Absorption. The ability allows him to eat anything from a living creature to material no matter how hard or toxic. The strength of the ability gained depends on the condition of what's eaten.
 * Wise Man's Grandson has the main character, Shin Wolford, who gets reincarnated with vague memories of his previous life. He learned to control his magic power and chantless magic from the Wise Man Merlin and Guru Melinda. Shin combines magic with the knowledge of modern science for powerful effects and new forms of magic. There is also how he uses Enhancement magic to modify clothes and accessories better than Guru Melinda. The application is made by using Kanji instead of the alphabet used in the world, which can give more options for customization.
 * Knight’s and Magic have the main character, Ernesti Kurata, who was a genius programmer and mecha otaku reincarnated into a world where magic and mecha called Silhouette Knights exist. He realizes that magic is like computer programming. Ernersti applies this to use high-level magic at an early age by reprogramming his own internal Magic Circuit with subroutines. He also uses this same knowledge to reprogram and improve the Magius Engine of a Silhouette Knight. There are also the inventions he has developed, such as a wand that can be used for close combat and innovations to the magical mecha.
 * Parodied in Kono Subarashii Sekai ni Shukufuku o!, where a shut-in NEET, Kazuma Sato, dies from shock after mistaking a tractor for a truck while trying to save a girl. He is offered the opportunity to reincarnate by the goddess Aqua into a world that’s like an RPG under siege by the Demon Lord. Along with reincarnating, he then is offered an advantage to use in the new world. Kazuma then chooses Aqua as his bonus, and another goddess recognizes it as official, then they both get teleported to this world.
 * Konjiki no Word Master has five teenagers summoned, but only four of them are titled as the heroes who are there to save the kingdom. Each hero has their own advantages, like affinities for all elements of magic or talented with physical actions. The fifth is the main character with the title, Innocent Bystander, but can use the unique Word Magic. The magic has him draw Kanji and apply the meaning of it as an effect.
 * World Strongest Rearguard: Labyrinth Country and Dungeon Seekers have a man named Arihito Atobe reborn as a Seeker in the world called Labyrinth Country. After getting his Seekers License and chooses the Rearguard job, which is different compared to the other jobs like Valkyrie and Priestess.
 * Death March to the Parallel World Rhapsody has Suzuki Ichiro, who was a 30 programmer that died from exhaustion and ended up reincarnated into a younger body. After seeing a game screen, he realizes that he was given the name Satou along with the three use power of Meteor Shower. He then gets attacked by an army of lizardmen and then uses up Meteor Shower against the battalion and levels up to 310.
 * Downplayed in So I'm a Spider, So What?, where people who reincarnate into the world with the skill, n%I=W.
 * Deconstructed in Re: Zero, where the protagonist Subaru Natsuki has the ability he calls Return from Death when he is transported to a fantasy world. He can return to a previous time or a ‘save point’ after death. Other than that, he is an average human with no other supernatural abilities.
 * That Time I Got Reincarnated as A Slime has Satoru Minami gets reincarnated after getting killed by defending his subordinate from getting stabbed. Due to how he died a virgin, he gained the Unique Skill of Great Sage along with other skills such as immunity from pain, resistance from electricity and heat such as fire and ice.
 * In Another World with My Smartphone, where the main character, Touya Mochizuki, is accidentally killed by God and reincarnated into another world. He is granted a body with superhuman abilities and affinities for all seven magical elements. There is also his smartphone that can be charged with magic power and can access the internet from Earth.
 * Overlord has the protagonist, Suzuki Satoru, being transported to the New World as his Yggdrasil character, Momonga, along with the guild headquarters and all the NPC subordinates. The New World acts much like the game, along with how his character has been leveled up to 100 before being teleported.
 * Isekai Cheat Magician has the two protagonists, Taichi and Rin, who are summoned to the new world and gain new powers. Taichi is gifted with a massive amount of magic power, which can be used to gain superhuman physical abilities. Rin gains her own reservoir of magic power while also showing affinities for earth, wind, fire, and water magic. She does show a lower capability than Taichi but uses her knowledge of physics to enhance her magic.
 * Reincarnated as a Sword has a 30-year old salary man show was killed in a driver who was texting while driving and reincarnated into a living sword. He can gain new skills by slicing the magic crystals of monsters. These skills can be used by anyone who wields him along with the stats he carries adds to the wielder. One unique feature from other weapons is his Mana Conductivity ranked at A, which means that his weapon sharpness and power can be increased by 200% when coated with mana.
 * Fushigi Yūgi: Every girl who is summoned into the world inside the book The Universe of the Four Gods is given three wishes -- but they are required to be Selfless Wishes.
 * Played with in Saga of Tanya the Evil has an HR manager dies and encounters a god-like being known as Being X. After a conversation on faith in deities, Being X reincarnates him into another world currently going through a war. He is reborn as a girl named Tanya in an imperialistic country surrounded by hostile neighbors; the difference is that magic is involved with warfare. After taking a magical aptitude test, she then becomes a candidate for the Empire's Imperial Armed Forces. She is also the only one who can use the Elenium Type-95 which is an unstable magic core and the only one that can use it without exploding as a 'blessing' from Being X.
 * In The New Gate, Shin managed to defeat the final boss of a VRMMO, The New Gate, that was a game that trapped people while if they die in the game, they die in real life. Before he could log out, he is sent through a gate and finds himself in an actual fantasy world similar to the game. He then learns the titles he gained after finishing the final boss can break restriction on all stats, doubles his current ones, and grant immunity from controlling effects.
 * The Ends from Drifters are historical figures from various points in Earth history that are brought to the fantasy world. They are people who suffered trauma from events in their life and have become twisted. They have supernatural abilities such as mind control, necromancy, cyrokinesis, and biokinesis. Averted for the Drifters, who are normal humans but share the trait of acting on their ideals and goals.
 * Tagami Yuseki from World Customize Creator, is summoned to another world by the Evil God and granted a Divine Art, a power a person can be blessed with from a god. This power allows him to customize any objects' attributes where he can even grant powers to them.
 * The Familiar of Zero: when Saito is summoned as a familiar into Louise's world, he gains the ability to use any weapon with great skill, from a simple broadsword to a fighter aircraft.
 * Played with in Magic Knight Rayearth: All three of the girls summoned to Cephiro have their magic unlocked, but that was done almost as soon as they arrived by a powerful mage, not as a side-effect of the summoning.
 * Tensei Shitara Dragon no Tamago Datta - Saikyou Igai Mezasa Nee has the main protagonist reincarnated as a barely unhatched dragon egg with certain skills. One is God's Voice that allows him to speak to a god, and the other is Walking Egg that gives more experience points from any monster he kills.

Literature

 * In John Carter of Mars, the titular character travels to Mars by having his soul teleport through space and gains a new body. Due to the lower gravity, he gains superhuman agility and strength.
 * Everworld where the teens can bring modern technology and knowledge to Everworld where they give them advantages such as trading a recipe for gunpowder or using conventional weaponry.
 * In The Scum Villain Self-saving System, Shen Yuan, who before his death and transmigration was an ordinary (albeit sickly) person, discovers that he has full access to the powers Shen Quinquiu (the body he is occupying right now) has, and also the knowledge on how to use those powers.
 * In the Chinese webnovel Release That Witch! and its webmanhua adaptation, the protagonist is an civil engineer that after dying of overworking finds himself transmigrated in the body of Roland, a prince from a world that has both a medieval level of technology and the presence of "witches", women with magical abilities that are prosecuted for it. The only boon the character receives was that, before taking over him, the original Roland has a fame of being very eccentric and had an already stated admiration for witches, which serves New!Roland perfectly to create plans to uplift this world's technology and recruit witches for his plans without creating suspicions for a long while, as everything he does is written off as yet another eccentricity of the prince.
 * Similarly, in the Chinese romance webnovel Transmigrator Meets Reincarnator, the heroine transmigrates to a novel taking place in a very old dynasty that didn't know modern Chinese cooking methods or ingredients... which suits her fine, because in her previous life she was an entrepreneur and an amateur chef, so she can basically use her abilities to win people with her unique and delicious (for that era standards) dishes, and create profitable business. Her other real boon are her knowledge of most of the novel's plot, and that the character she transmigrated has just married into a powerful and influential family and her husband abandons her almost immediately, which means that she knows which characters are trouble (and so she avoids them) and has a lot of liberty to do her business at her pace.

Video Games

 * Fantasy Boyfriends: Legends of Midearth game has a young man being summoned as the legendary hero that is the only one that can wield the sword that can defeat the Demon Lord.
 * Tokyo Afternoon Summoners takes place in an alternate Tokyo where people from 23 different worlds are summoned due to an app and are called Transients. Each Transient has a Role and is summoned with a Sacred Artifact that gives a Rule to their Transient. A Rule is a power that correlates to the Role of a Transient. An example would be a person given the Role of Fighter, and their Rule is Infinity.

Web Comics

 * I am the Sorcerer King webtoon has people called Awakened who gain a superpower and become connected to the Akasha System along with fighting monsters that come from portals. Lee Sunghoon awakens to his past memories and magic of being the reincarnation of The Great Sorcerer, Kurataurus, who is from another world. The incident happens after being attacked by a monster and becomes one of the Awakened which connects him to the system.

Western Animation

 * In the opening credits of the 1980s Dungeons and Dragons cartoon series we see Dungeon Master gifting the trapped teenagers with the magic items that grant them powers (and character classes) they need to survive.