GameBox: Far Cry 4 Easter Eggs #1

Far Cry

The Gamebook piece of loot includes a reference to the original Far Cry game in its description. "In this riveting Choose A Path Adventure, YOUR choices determine if Jack Carver successfully escapes the deadly island of Dr. Krieger."
Hurk mentions one of his "tattoo bros" is Jack.

You will sometimes find malaria pills in loot, referencing Far Cry 2.
You will sometimes find conflict diamonds in loot, with the description describing that it comes from Bowa-Seko, a main location in Far Cry 2.
The GPS locator given to Ajay by Longinus in his first mission is the locator from Far Cry 2 with the screen smashed.
Longinus himself is implied to be either Leon Gakumba or Prosper Kouassi.

The Knock-Off GPS loot item's description refers to Rook Island, the location of Far Cry 3's events: "A cheap copy of an Elcano hand-held navigaton device. Comes pre-loaded with a map of Rook Island, wherever the hell that is."
In the Second mission with Willis he mentions, "You're not like the last So. Cal douchebag I babysitted during my last op." This is referring to Jason Brody.
The Maimed Wahine loot item's head may be Vaas Montenegro's. The description: "The hula girl's head has been replaced by an insane-looking man with a mohawk."
After completing one of the Armed Escort missions, which entails delivering a truckload of contraceptives and disease test kits, the driver remarks that "now we won't have to listen to those soldiers complain about how it burns when they piss". This likely refers to common pirate idle dialogue.
During meeting before attack Royal Palace, a Female Golden Parh Warrior use Rook Island map .
The description of the loot item "flash drive" states that it probably contains pornography and drug formulas. This may be a reference to the collectible memory cards in Far Cry 3, all of which were regarding drug formulas.

After liberating or rescuing a local from Pagan's forces, a villager might say "Boy, that escalated quickly. I mean, that really got out of hand fast!". Referencing the popular quote that has also spawned a meme.

While talking about Pagan Min's heroin filled plane Rabi Ray Rana mentions the name Walter White.

The Hypodermic Needle loot item includes a reference to BioShock and its EVE Hypos in its description: "Filled with glowing liquid. If this were a failed underwater utopia, you wouldn't think twice about jamming this in your arm."

In one of the houses with Yalung mask murders and a part of supply delivery mission, you will find a dead man with a red plastic bucket on his head and an arrow stuck in his knee. Bucket on the head in a popular Skyrim user exploit, with "arrow in the knee" is the infamous Skyrim guard spoken line.

The 'Photo of a Dwarf 2' loot item has the description "A picture of a naked dwarf with a nasty facial scar. Winter's not the only thing coming." This is an obvious reference to Tyrion Lannister, a dwarf who received a face wound during the Battle of Blackwater. It also references the motto of House Stark, 'Winter is Coming'

Source: www.wikia.com