Easter Eggs in Black Mesa

Has anyone seen this video? Its really interesting. When I finish the game play, I will go back and see if I can find all of the easter eggs mentioned.

https://www.youtube.com/watch?v=WSC3jEKpVQk

Founded in 2004, Leakfree.org became one of the first online communities dedicated to Valveā€™s Source engine development. It is more famously known for the formation of Black Mesa: Source under the 'Leakfree Modification Team' handle in September 2004.