Soccer Ball Easter Egg
On Mission 4- Meridian Station head to the left hand side of the station until you found a vending machine, hit the buttons several times and then a soccer ball is created. Locke and Buck play a game!
Vending Machine Easter Egg
On Mission 3 - Glassed after exiting the building, you can find a vending machine inside of a room to the right hand side on the ground floor. Interact with it and it will spawn a magnum, Shotgun and SAW.
If you have any more Halo 5: Guardians Easter Eggs, post them!