In Operation Flashpoint and Resistance there are quite a few Easter Eggs to be found.
The most popular Easter egg in Operation Flashpoint are the Christmas trees. When your computer clock changes to December 25th the small spruce trees in OFP light up like Christmas trees with nice presents and decorations. See here for a config.cpp to access this model.
Lenin photo in guardpost编辑
In the guardpost building you can see through a small opening, a photo of Lenin on the wall.
Poster of Stalin编辑
In the barracks buildings found on Kolgujev, in the hallway you can see posters hanging and one of them is a picture of Stalin.
Perhaps this object is just decoration or did BI plan to have it in OFP but wasn't able to finish it in time? We will never know. You can view the site at grid HE77 on Everon.
Man with Briefcase?编辑
Maruk hinted to the community about a Man with Briefcase in their site? What kind of secret is hidden behind this?
Hummer with names above wheels编辑
Above the wheels of the Hummer you can see "DnA", "Sith", "AnG" & "rUiZ"(?) written on it. These are the names of some of the developers for BI.
Nogova Gas Station编辑
This one is quite scary, you can see an evil smiling face on the poster between the pumps, with some czech text on it (english translation of that text is: "You'll be blissful only with us."). Name of the gas company is also parody to real czech company, Benzina. The evil smiling face is actually a BI employee, Viktor Bocan.
Elevator Shaft Text编辑
As you reach to top of the highest aparment building you can see something written on the wall in the elevator shaft.