In the "High Tension" map, go to the second floor of the shopping mall. One of the stores is named "Ishimura", which is a reference to the "USG Ishimura" mining spaceship in Dead Space.
In the "High Tension" map, go the police station to find a few pink donut boxes on a folding table in the garage bay. While looking at the boxes, press [Spot] to shout "donuts spotted!".