Sensor Character

A Sensor Character is a character with a sixth sense that they can use to detect other characters. Telepaths reach out to look for the minds of other characters. Others might detect lifeforces or auras, or perhaps a specific type of phlebotinum. A more realistic version might be a character with enhanced hearing or sense of smell who can track others down. Depending on the setting, it might be the special skill of a single character or a basic secondary power anyone can use.

Compare Aura Vision and Third Eye. For the technological counterpart, see Everything Sensor. May be related to Enemy Scan. See also The Force Is Strong with This One

Anime and Manga

 * Bleach It's a basic secondary ability of anyone who is spiritually aware to be able to sense the reiatsu of other spiritually aware/active beings. Depending on their level of exposure to the spirit world, however, will depend on how well they can interpret and react to it. Even characters who are said to be bad at reiatsu-control have no problem sensing the reiatsu of others unless anyone is actively working to suppress their reiatsu.
 * In the first filler arc, mod souls which could specifically sense the Bount were introduced.
 * Early on in Dragonball Z, the ability to sense power levels without a scouter or other device was part of what separated the good guys from the bad guys. As the series went on, more and more people were able to do it on their own.
 * Certain ninja in Naruto, actually called sensors, have the ability to detect the chakra of other ninja. This is also one of the innate abilities of ocular jutsu, namely the Sharingan and Byakugan.
 * Claymore features several characters whose uncanny abilities at sensing the yoki (demonic energy) have led to them being mainly used for remote observation of other Claymores and yoma. Case in point: "God Eye" Galatea and "Tracker" Dietrich.
 * In Cyborg 009, one of the nine cyborgs is a woman whose only special ability is super-senses at long range. The nine are intended to function as a unit, and her job is to detect incoming threats (though she does get a laser gun to defend herself with).
 * In Fullmetal Alchemist, Xingese warriors like Lan Fan have the ability to detect the Qi of others. Lan Fan can detect the homunculi because of their twisted life energy.
 * In Darker than Black, emotionless children known as 'Dolls' are used for remote scouting and searching. They're capable of sending their senses out through some medium - the exact medium varying from Doll to Doll. The most common type - used en-masse by the antagonists - sees through powerlines and electrical appliances. Other types we've seen can see through any surface of water, or any surface of glass. Often, they work in concert with Contractors, spotting targets for them.
 * Shamal of Magical Girl Lyrical Nanoha has this role in addition to being The Medic. Her ability to detect enemies is advanced enough that she could spot someone hidden from more conventional magical and technological sensors employed by the TSAB. Other characters can also use spells like Area Search.
 * Inuyasha: Youkai can sense the aura (jyaki) of other youkai. Spiritually capable humans such as monks and miko can also sense these auras. This also applies to humans who don't have spiritual abilities but who have been trained to deal with youkai, for example, professional youkai-exterminators such as Sango and Kohaku.

Comic Books

 * Pretty much any telepathic mutant in X-Men (Prof. X, Jean Grey, Emma Frost...) can fill this role. On the same subject Wolverine's senses are so high tuned he can recognize and track people by individual scents -this ability also allows him to see through shape-shifter disguises.
 * The Marvel Universe character Rachel Summers was forced to use her psionic abilities to detect and hunt down mutants in a dystopic alternate future.
 * Dr. Kate McCrae from "The Black Hole" is so ESP sensitive that she can communicate telepathically with V.I.N.CENT, a robot! (Unless it's a case of They Just Didn't Care)

Film

 * All Force-sensitive individuals in Star Wars can sense the presence of other Jedi, Sith, etc., as well as powerful emotional outbursts from normal people.

Literature

 * Over the course of the first few The Wheel of Time books Perrin's connection to wolves grants him a sense of sight and smell on par with that of a wolf. He routinely notices people walking up behind him by catching their scent before they make a sound.
 * Wizards in The Black Company series can learn to be those. Actually, the company owes most of their victories to Boring but Practical applications of magic (as opposed to Stuff Blowing Up favoured by the villains )
 * The Harry Potter series has the "Homenum Revelio" spell, which detects the presence of humans in the vicinity of the caster.
 * In The Dresden Files, Harry can sense the presence of magic in others. He can even tell how skilled a user the other person is from minimal contact.

Live-Action TV

 * Deanna Troi in Star Trek: The Next Generation worked this way when she was well-written.

Video Games

 * Persona 3: Mitsuru and later Fuuka, with their ablities to dectect Shadows crossing with Mission Control.
 * Persona 4: Teddie and later Rise

Western Animation

 * In Justice League, J'onn J'onzz often fulfills this role, thanks to his telepathic abilities.