Castlevania: Lords of Shadow Easter Egg - Various Little Eggs

OK so, in the first levels, in the forest, you will come across a giant, dead tree. Somewhere near that tree lies a fallen knight. Register him and you´ll find a scroll giving you details on that dead tree. You´ll find that the tree was in fact the Great Deku Tree!.

This one´s a Portal reference: In the last levels of the necromancer´s realm there is a lot of puzzles involving portals and one scroll describes it´s sorcery as "Aperture Magic". A clear reference to Aperture Science from portal.

A reference to MGS. Before the Butcher boss fight, you hace to reach a hole in the wall, wich leads you to a narrow crawl space. Just when you reach it, a very familiar MGS tune will play.

One of the special moves the main character can use is called "Dragon Uppercut", and it´s execution looks strangely familiar to Ryu´s shoryuken froms Street Fighter.

Last one is a reference to Day of The Tentacle: Begin the "Abbey Tower" level and immediately walk out to the left from the corridor you are standing in. Look for an old wooden cart against the side of the building. Destroy the cart, and there will be a fallen comrade on the ground underneath the debris whom has a note attached. Pick up the note. It makes reference to his sister Laverne and brother Bernard, and it is signed by "H.", which refers to the other main character known as Hoagie.