I've gotten ever single one except the one in the weird orange half life fluid chamber thing? I'm completely stuck about this one!?!

but for what you asked i think the coolest is the piano one. literally just play the first few notes of sans's theme lol

You just hit it until it breaks. It has 1000 HP (according to the Barricade SWEP, at least) so I think that's 100 hits with the Crowbar.

I've gotten all but 1 and I don't know which one. I'll just list all the ones I can remember finding out here.

* Indiana Jones Temple Escape
* Cleaning Up Litter In the Park
* Lever Hallway Puzzle
* Megalovania on Piano
* Top of Big Tree
* Water Cooler Painting
* HEV Room Container (Smash It)
* Tiny Water Cooler (Can't remember where I picked it up

I know there's more here.

to be honest idk how to the piano part, i know what to do, but idk how to do it and what notes on the board. Like need 1 through how many their are in their order to know since idk how to.

October 님이 먼저 게시:

* Indiana Jones Temple Escape
* Cleaning Up Litter In the Park
* Lever Hallway Puzzle
* Megalovania on Piano
* Top of Big Tree
* Water Cooler Painting
* HEV Room Container (Smash It)
* Tiny Water Cooler (Can't remember where I picked it up

Tiny one is the Indiana Jones Escape, so they're the same one, but the trigger is actually the boulder reaching the 11th waypoint of its path.
Water Cooler painting is in the dark void room near the crossroads, I assume?

There's also:
* Construct Dark Room Candle
* Cylinder Maze
* Top of MGS3 Ladder

Found all 10 watercoolers:
1. Snake Eater ladder
2. Play the first few notes of Megalovania on the piano (not the grand piano, the piano keys room)
3. Clean up litter in the park (there should be a no littering sign)
4. Indiana Jones temple
5. HEV room container
6. Maze area with large cylindrical gray pillars
7. The four levers
8. There's one surrounded by chairs near the main spawn area
9. On top of the big tree
10. The candle room (you have to sit in the chair for a couple minutes)

how play megalovania on big pian keys

I'm completely stuck at piano too

okay seriously how do you play megalovania on the piano keys like what specific keys are you meant to play please i am going insane from trying to just brute force it

any luck with the piano?

Piano notes are:
DD ^D A

Start with the D on the far left side, go up an octave with the third D and then use the A in between them

wiimeiser 님이 먼저 게시:

October 님이 먼저 게시:

* Indiana Jones Temple Escape
* Cleaning Up Litter In the Park
* Lever Hallway Puzzle
* Megalovania on Piano
* Top of Big Tree
* Water Cooler Painting
* HEV Room Container (Smash It)
* Tiny Water Cooler (Can't remember where I picked it up

Tiny one is the Indiana Jones Escape, so they're the same one, but the trigger is actually the boulder reaching the 11th waypoint of its path.
Water Cooler painting is in the dark void room near the crossroads, I assume?

There's also:
* Construct Dark Room Candle
* Cylinder Maze
* Top of MGS3 Ladder

Ah, I probably just didn't wait long enough inside the chair in the dark room with the candle

October 님이 먼저 게시:

Piano notes are:
DD ^D A

Start with the D on the far left side, go up an octave with the third D and then use the A in between them

I've tried searching online for piano key references and I made a lot of attempts, still not getting the water cooler
Can you just tell the combination in numbers for the keys?
It's more clear that way

I think I figured it out
second key 2 times, ninth key 1 time, sixth key 1 time