Jack Sparrow (Pirates of the Caribbean) and Lara Croft (Tomb Raider)

This should be pretty obvious, Korosensei is wearing a hidden leaf headband from Naruto when he teaches Terasaka about who know what.

Soul eater and Fullmetal Alchemist in Barakamon. I just found this on google image even though it's not Assassination Classroom, related.

Watamote has a Kuroko no Basket reference

Why is Kuroko's hair black?

Yugioh in No game no life. Seriously, there are too many easter eggs in No game no life and I do not want to go over every single one. *^*

Dragonball in Assassination Classroom

Shiro reading Shounen Jump (We expected that from Fuwa already so this is a slight surprise)

This can be called an easter egg, I guess?

Kuroko and Akashi from Kuroko no Basket look similar to Nagisa and Karma from Assassination Classroom.

(This is not an anime but it is sort of like a easter egg. )

The game LOLOL played by Yoosung is a reference to LOL, which means League or Legends while LOLOL means League of Loneliness of Life. Poor poor Yoosung without a girlfriend.

By this point, I was distracted by Kuroko no Basket phone covers XD. Too bad I don't have enough money. ;-; .

Anyway, these are all the easter eggs I can find so I challenge to see if you can find anymore!! ^-^