Research secrets
Halo Reach:Buck and Monkey
This secret can only be found in Halo reach when you hit the Left D-Pad button at a certain time during a cut scene doing this will result in you seeing Buck grooming the Monkey like creature and eating bugs from its hair.
Five nights at Freddy's 4 :Phone guys message.
On the 4th night in five nights at Freddy's 4 you can hear the phone guys first message to the player of the first game you can only hear it though if you Listen to the audio backwards other wise it will sound like gibberish.
Five Nights at Freddy 4; Family pictures.
In Five nights 4 in the left corridor from the child's room you can see family photos of Scott Cawthon (the creator of the game) and his family. Scott is know for putting clues in his game which people pass of as Easter eggs when there is actually more to it because he doesn't put random things for no reason he is leaving secrets for us to find and help us figure out the final story. People speculate that the house the 4th game is set in is Phone guys house because Phone Guy is voiced by Scott this is further backed up by these secret pictures.

Resident Evil:Jill sandwich.
In the very first Resident Evil when you play as Barry and Jill There is a scene where Jill is almost crushed from a lowering ceiling, luckily Barry rescues here and say's one of the most famous lines in Resident Evil "You were almost a Jill sandwich. Later on in another Resident Evil game the developers but a burger joint in called Jill's Sandwiches.

Game Of Thrones: Coldplay drummer
Only seen for a short moment in the Episode Red wedding where two Stark's are killed you can see the drummer of Coldplay playing in the background.
Game of Thrones: The Mountain
Not many people know this but the actor for the Mountain changed three times The original was Conan Stevens, then there was Ian Whyte and Hafthór Júlíus Björnsson.
Game Of Thrones :Arya
Arya has to hide her identity so she will not be killed as well as be recognized she joins the faceless men where she hides. She is one of the last Stark's, and if anyone was to find out they would most likely kill her.
Game of Thrones:The down fall of Robb Stark
In the scene shown below it looks like a normal strategy showing the Stark's the Bolton's and The Freye's which look to be overpowering the Lanister's but in all actuality it represents the Stark's
being surrounded by there supposed allies.