3 white flowers music EE:
You'll need to interact with 3 white flowers around the map:
1 is near the waterfall to the far left
1 is near the key door
1 is near PAP

Jukebox music EE:
Don't know all the locations, but if you interact with all of the colored jukeboxes, it plays a song.

Anime posters EE:
Again, there's a lot and I didn't write down all of the locations, but if they're in reach, you need to interact with them, the ones that aren't in reach need to be shot. There is 1 poster that you can't interact with until after the clock step of the main EE. Once all have been interacted with/shot you will gain Perkaholic.

Jumpscare:
If you look in the window to the left of the bank and aim and shoot the teddy bear, there is a jumpscare.

Hole in the wall:
Once you complete the main EE, you must have bull ice blast (double jump perk) and you'll need to start the fling trap. Just use the fling trap and double jump into the wall.

Targets EE:
There are 3 targets in the creek areas under the bridges near spawn. Shoot all 3 with bullet weapons (not sure if they need to be packed) and you'll be awarded 1,200 points.

Weapons:
Once you complete the main EE, it will unlock:
Resulsor (basement)
All 4 bows (2 near spawn, 1 near key door, 1 near PAP)
Blast-o-matic (in the bar)
and the Blundergat (saloon-looking building near spawn)

Acid/Magma-gat:
You'll need 3 parts to build the Acid-gat:
1 is near the key door in a big puddle
1 is near wunderfizz behind some barrels
1 is behind the last car before the edge of the map near the bank

Magma-gat: The forge for the magma-gat is located in the corner of the room to the right of the waterfall by spawn.

Shield:
1 part outside the bar on the deck
1 part right next to the RPG buy and mule kick
1 part in the church

Buyable ending:
Once you complete the main EE quest, you need to go to the basement, sit all of the keycards down on the little thing near the table, go to the back room and open the final door. Interact with the panel and it will start a countdown (I think it's 2 minutes) and you must make your way up by the train to the helicopter that will be waiting for you to wisp you away lol.