Heart Light

As dictated by the Rule of Cool, aliens, robots and magical creatures in fiction have a tendancy to give off light from various places on their bodies, including eyes, mouths, veins, and markings. This trope is about creatures who have a single light source on their chest, which is usually either centred straight in the middle (as is the case with most robotic examples) or off to one side if it represents their actual heart. If the Heart Light shoots some sort of beam, it's a Chest Blaster.

"Turn on your heartlight

Let it shine wherever you go

Let it make a happy glow

For all the world to see"

—Neil Diamond, "Heartlight"

Some forms of Chest Insignia may overlap with this Trope if they glow or emit light.

Examples of Heart Light include:

Anime and Manga

Sailor Moon's final form consists of her having wings and a Glowing lotus symbol on her chest.

Comics

Iron Man's power source resembles one of these.
The circles on the armor of The Mighty Thor are sometimes portrayed as glowing.
The post-Annihilation costume of Nova has these all over the place.
As shown in the page image, the Alpha Lantern Corps makes use of these. For Bonus Points, most of them are both aliens and robots/cyborgs.
- The Green Lanterns themselves sometimes employ this when the lantern symbol on their costumes light up.

Film

ET the Extraterrestrial has the organic variant, and is probably the Trope Codifier.

Live Action Television

Ultraman, no matter the incarnation, always has one of these. The faster it's flashing, the closer he is to running out of power.

Music

The song by Neil Diamond quoted at the top of the page is the Trope Namer, having been inspired after seeing the Trope Codifier "E.T."

Toys

All the people of the Matoran Universe in Bionicle have these, at least according to the books and movies. They're even called heartlights.
Similarly, the Hero Cores in Hero Factory.

Video Games

Ganon in Twilight Princess has a white, glowing scar in the middle of his chest, left over from when the Sages tried and failed to execute him with a sword.
Ghirahim in Skyward Sword, during Link's third battle with him, develops a similar one, and for similar reasons.

Western Animation

The symbol on Captain Planet's chest.