Middle Finger to the dumbass rat that tries to bite you:
To do it you must fail the quick action by press any other button when it happens.
Sandcastle Easter Egg
This sandcastle is found in Metro, on the first stage, at the playground.
It is the same one from BFBC2 and BF1943. Also there is a Swedish flag on it, where the DICE dev's were from.
Photo Booth Easter Egg
Hidden Song (Battlefield 3 Easter Eggs & Secrets)
You may have come across some XCOM Stations that have quickly scrolling text. Think its military related? Think again… The text are actually the lyrics from a 200 year old Swedish folksong.
MIRROR'S EDGE 2 :Faith’s Bag (Battlefield 3 Easter Eggs & Secrets)
You can locate the bag that Faith carrys on her from Mirror’s Edge. Could this be a hint at Mirror’s Edge 2? Or just a clever Easter Egg? In addition to these hints at Mirror’s Edge, there are many other Mirror’s Edge references in Battlefield 3. Signs exiting from the Metro Station point to “Av. de Faith Connors” which is a direct reference to Faith, the main character of Mirror’s Edge. And then you consider that the Metro Station itself is called “Rue Catherine”, the pieces start to come together. “Kate” was the name of Faith’s sister.