Odrin from Witcher 2, it is in W3(Novigrad), and also on a board in Toussaint....

There is no cow level!

PT from Deadth Stranding A reference to Silent Hill found in Sam's Shower. It will scare you one more time.

My favorite easter egg is in CrossCode. In the Rhombus Square location, there is occasionally a car that passes by, perpetually drifting and blasting Eurobeat music, which is a clear reference to the anime, Initial D.

I'm not sure if this is considered as secret/egg, but more as a reference. In Borderlands 2, the last phrase Lilith is "Yea. Heh - no rest for the wicked.", which is referring to the opening song for the first Borderland game Cage The Elephant - Ain't No Rest For The Wicked.

He lives!

Mr. Toots from Red Faction Armaggedon. Makes me laugh all the time. Shooting a rainbow beam from a pony's rear. Makes no sense and it is hilarious.

One of my favorites is also one my first:

I used to play the Sierra adventure games a lot, like Police quest and Space quest, originally missed out on LucasArts style adventures for a long time. So when finally playing The Secret of Monkey Island for the first time, it was rather fresh to me that you couldn't seem to die by making the wrong choices. When you finally arrive at Monkey Island, there's this part on a mountain cliff where you can fall off, and oops, you died, Sierra adventure style.

.. only to be bounced back by a rubber tree.

https://www.youtube.com/watch?v=1-_-QxerYno

The dancing zombies in Thief 2: The Metal Age. You have to toss a spying orb over a wall in the beginning of a level.

It's been mentioned before, but it is such a great and memorable Easter Egg as it encouraged exploring and try to get into or look into inaccessible spaces in many games using only the tools the game gives you. It is great fun trying to figure out how to get into places you shouldn't be or see in other games, even if there wasn't much there.

The legendary Alarus Extension for instance is a very memorable Non-Easter egg in Thief: The Dark Project's Bonehoard level. For years it was an online joke. It is just a rectangular space behind a hole that you could almost, but not quite reach after many frustrating attempts. The tales that were spun about what lay beyond.... but it turns out you can actually get into the small space in the game with some incredibly precise jumping and mantling.

Another very memorable experience is exploring the background scenery in Deus Ex's Hong Kong, where you can cross a bridge and discover a mysterious tunnel in the ground if you have enough speed and jumping power.

You can also explore the background scenery/town of the same Thief 2 level the Easter egg is in with some creative jumping and mantling!

The strange locations in other games and the challenge and thrill in getting there or seeing them, even without an Easter egg at the end, are too numerous to list. Yet, here is where it all started, at least for me, and that's what makes this one so special.

Not the greatest, but when I think about easter eggs, it always to my mind the first I found in my life: John Romero's head in a stick, on Doom 2. A true classic!! :D

The easter egg in The Witcher 3 which references DRM. It is the quest called "The Tower Outta Nowheres", where you will find a book called Gottfried's Omni-opening Grimoire. Here is an excerpt from it: "(...) DRM thus makes for an extremely effective and near-unbreakable security measure - but you are in luck, for you hold in your hands the key to bypassing it, namely the present tome, Gottfried's Omni-opening Grimoire, or GOG for short. In the pages to follow you will find innumerable methods for deactivating DRM, or, even better, bypassing it altogether (...)"

Overall very fun quest that is all about problems with DRM.

It's gotta be Gnome Chompski dude! Getting the achievement in Left 4 Dead 2 by carrying 'em to safety was easy enough, but afterwards I loved it so much I wanted to buy a Gnome Chompski, put 'em in my garden and that turned out to be an impossible task D: Someday...I'll be forced to make my own. I just need it, cus reasons...maybe carry 'em to cons.

Spoilers for 'Sherlock Holmes: Moriarty's Return'.

In 'Sherlock Holmes: Moriarty's Return' there is a red pentagram hidden behind a trash bin.
Holmes:'Watson, does this remind you of anything?'
Watson: 'Russia. I don't know why, but it reminds me of Russia'.

Grand Theft Auto 4 is one of my favourite games, and i absolute love it. It's one of the hidden gems in the gaming history. there is a island in the game called happiness island, where you can go and see the Statue of Liberty known as Statue of happiness in the game. If you take a helicopter up there, and look for door sandwiched between two signs that says "no hidden content this way" and if you walk on in. Inside the statue you'll find a giant, beating heart.

My favorite easter egg is the dancing werewolf in Vampire: The Masquerade - Bloodlines. It's actually a two step easter egg, but maybe it only ended up this way because I connected both parts in my Unofficial Patch ;). The first part needs you to open and close doors in the Luckee Star motel map many times, then a dancing werewolf as huge as King-Kong will appear in the backyard. The second part makes the same werewolf appear regular sized at the ending of the game and the player will dance together with it while the credits roll!