Bread
You can gain 5% health by eating bread, you can find it on tables in several levels, like Operation Repunzel, or Yard by Yard, to indicate you have eaten bread, a measage will come up and say, "The Bread is Delicious!"
Poor Chef!
During the course of the game you will encounter the Chef several times, in the first encounter he appears perfectly healthy, but gradually he starts looking worse, with tears in his cloths and he will become bruised!
Panzerknacker Tank Eater
You can see this hidden secret on the Golden Lion level (Needle in a Haystack.) Somewhere in the pub at the end, you can see it through one of the doors.
Wierd
In Nijmegen Bridge (Several Bridges too Far) if you turn around and shoot the other American solider with a sniper rifle in the face, it will show the damage without killing him, aim at his face and he will continue smiling even if you blow off his lips!