Three items in Horizon: Zero Dawn are references to Hideo Kojima’s game Death Stranding.
Once you perform the story quest “The Proving,” go to the All-Mother ruins to find the Stranded Figure item. This is a doll that looks like the doll in the second Death Stranding trailer.
During or after the story quest “The Grave-Hoard,” enter the Grave-Hoard and follow the left wall until you reach the first room with enemies. You’ll find an item called the Stranded Necklace. This necklace matches the dog tags worn by Norman Reedus’s character in the first Death Stranding trailer.
Finally, after the story quest “Deep Secrets of the World,” enter the Zero Dawn dungeon and head to the southwestern area of the map in order to find the Stranded Shackles. These shackles resemble those also worn by Normun Reedus’s character in the first Death Stranding trailer.
The symbol used for these items is also the helmet silhouette used in the logo for Kojima Productions.
These Easter eggs are all likely nods to the fact that the developer (Guerilla Games) gave Kojima their Decima game engine to use for Death Stranding.
Near the mining camp after you find the War Chief, you can find two rabbits named Jazz and Jack. This is a reference to the 1994 game Jazz Jackrabbit. The primary coder of Jazz Jackrabbit was a programmer named Arjan Brussee, who went on to be the co-founder of Guerilla Games, the developer of Horizon.
One of the “ancient vessels” you can find is called the KZ vessel and depicts a “threatening red-eyed visage” that should be familiar to anyone who has played the Killzone series, also from Guerilla Games, since the image on this mug is a Helghast soldier.