I spent quite a while running around looking for these, and when I went to the guides / discussions noticed not much has been said about them yet. This is my first guide so if you don't like the formatting please leave a comment. Also I haven't found ALL the easter eggs yet so I will update it once I find the rest (or someone explains them in the comments). Please let me know if the map screenshots are not enough and I will add in-game screenshots.

Ordered by steam own % as of time of writing.

Semeicardia in the comments said they were able to unlock one of these in Evil God mode.

In the area with the dinosaur bones, center-ish on the map, randomly you might find a weapon crate with a parachute on it. Attack it until it breaks and it will have a flare gun in it. I think you get the achievement just by breaking the box, so once per run in case you're playing multiplayer and everyone wants it. The flare gun has a long reload time but it drops armor crates for 5 armor and sometimes weapon crates. Highly recommend to grab it using one of the 3 additional gun slots, or if going for a build without weapon (contact damage, summon, etc)

On the bottom right of the map, a little bit north of the teleport crystal, there is a cemetery with a death statue and a weird ritual star circle thing. I thought you needed to use the statue to summon enemies but it turns out you just have to hang around the circle and kill enemies for a while for the boss to spawn. The boss has an asian (korean?) name in dark purple letters. Kill it to get the easter egg. Only one person can get it per run as far as I know.

All I know about this one is you get it sort of randomly when using catapults. Your character will have green particles coming out of it if you grabbed whatever gives you the easter egg.

I don't understand the unlock conditions for this either. Me and my co-op partner got it while walking around the market, just normal backpedaling while killing zombies.

EDIT: Shino in the comments has figured it out. Leaving both comments here for convenience:

for death stranding, in the area you've circled on the map there's a corpse on fire (I believe it's near a bonfire), hit it with a water-type attack (water gun, adult water gun) to put it out and you'll get the egg/achievement.

I was a little off. There's a bonfire, when it's hit by a water attack (I managed to trigger it with the toilet equipment just now), the fire goes out, and a fireball calls enemies from the ground. I'm not sure which part of that triggers the egg. There's a decorative corpse there but it's not on fire.

The area is correct. It's the large fire in the eastern part of it, near the bridge.

Near the altar in the treasure room, inside the castle, there is a long hallway with tables on both sides and a corpse in a throne at the end. If you're missing armor, you can eat the food on the tables. I think it's about 10 pieces of food. After you eat all the food, two enemies with shields will spawn. You will have to destroy the corpse on the throne to remove their shields. Only one person can get it per run.

Around the teleport crystal in the forge, there is a giant hammer with a blue gem on it. Make the hammer get hit by some fire attack and it will go up and slam down. I believe it damages enemies, but to my knowledge no enemy has to be hit for it to give you the easter egg. Also I think the firewalk enemies also grant it. I'm not sure if multiple people can get it but I assume yes because I've seen the hammer slam more than once.

Dranseer in chat said: Ironforge only activated with electric damage for me?

So please keep that in mind. Thanks!

On the bottom left of the map, there is a wooden platform with 3 guillotines. The rightmost one can spawn in 3 ways as far as I know:
It might not be there, replaced by blood.
It might have a dummy with a radio for head that plays music. (This one gives you the Tailor)
It might be a horse.
If you cut the head of the horse it gives you the BoJack melee weapon and the easter egg. Only one person can get it per run.
There is a catapult near the war camp that lands right by the platform.

I am not sure if this is also related to the Beheaded Tailor.

I have only found this in the forge, but someone said they found it in the throne room. There is a transparent gun with no name on the floor. Once you walk over it you can see the name and pick it up to get the Easter Egg. I've always found it on the borders of the forge, near the lava, and seen it both on the top and bottom sides. Only one person can get it per run as far as I know.

Edit: as per comments, gun was also seen in the mines.

If you have trouble finding it, it still glows differently through walls like all weapons do. Also to my knowledge it doesn't drop from anything, it's just laying on the floor.

Edit #2: Another comment has mentioned they've found it somewhere else. I have not confirmed it but this leads me to believe it might spawn "anywhere".

My favorite one, I look for it every run just cuz I like it. Somewhere in the castle with the treasure room and the banquet you can find a gramophone on the floor. You will mostly notice the big piece where the sound comes out of. Interact with it and it'll play an awesome song and give you the easter egg. Only one person can get it per run.

This one is pretty fun. On the left side of the map, north of the BoJack platform and south of the treasure room, there are some houses with sunflowers. The rightmost house's door can be interacted with to get the easter egg. Multiple people can get it in a single run, though it looks like the door being interactive is random per run.

Everyone has probably found the Excalibur while walking around the map. To get it our of the rock, you have to bash enemies enough times for the rock to break, giving you the weapon and the easter egg. It took me a pretty long time to get, it seems to vary very widely based on luck. Only one person can get it per run.

Around the map there are a few campfires with a piece of meat above them. Use fire attacks on any of them, wait a bit for the fire animation, and then interact with it while you're missing armor to recover 5 armor and get the easter egg.

Right of the area with the Flare gun, or exiting the Forger, there is a cave with some shiny crystals. Around the exits of the cave you can find a pickaxe the game labels as shovel. Using the "shovel", bash the 4 red crystals inside the cave to get the easter egg. If you are not the host, you can still bash the crystals even if you cannot see them and get the easter egg. Ask the host to show you where the crystals are. Only one person can get it per run.

In the church altar, there are 4 tables with candles on them. They are basically in the 4 cardinal directions. One on the top left corner in after all the chairs. One on the bottom left, hidden by the walk (walk close to see through the wall), one in the long table to the right and one in the small room past the hallway going north. You have to turn the 4 candles on in a specific order (always the same order), and also relatively quickly (they go off). It's left, top, bottom, right. If you did it right, you'll see the capibara above your head dancing. Only one person can get it per run as far as I know.

BenBen can be found in the village/marketplace area on the bottom left of the map



I managed to find him near the houses but apparently he can be in other places. It took me longer to find because I didn't know what it looked like. I didn't take a screenshot but this should give you an idea:

The dog is dark colored, and it is trapped in a very shabby wooden box. The dog is laying on the floor looking downwards. Once you get close to it the tooltip says "Help".

BenBen has a helpful effect in-game if your hp drops to 20 hp, and only 1 player can unlock him per match.

Hobbit has it's own guide so I won't explain it here since that guide came before mine. :)