Here is a guide to get the Wunderwaffe, Thundergun, Magma Gat and the Alistair's Folly

Before you begin, you'll need to get both skulls and put them in the graveyard.

Guide for that is here: https://steamcommunity.com/workshop/filedetails/discussion/1663631538/1797403972745950479/

Wunderwaffe- When you open the panel outside the barn, insert 9 3 5 into it and a Wunderwaffe will appear in front

https://imgur.com/icmbWkP

Thundergun- Again, quite easy. Just kill doc Brown when you open the barn, you have a certain amount of time before he disappears.

https://imgur.com/IG2Cwjh

Magma Gat- There 5 furnaces around the map, simply knife them.
1) Hotel - https://imgur.com/n9m2BHw
2) Sheriffs office - https://imgur.com/72vs1Ed
3) Barn - https://imgur.com/XHolNFo
4) Saloon - https://imgur.com/rwAdPHU
5) Around blacksmith (In spawn) - https://imgur.com/DsBMadX

You'll hear an audio cue when you knife them all, in the last location a fire place will turn on to which you can place your blundergat (Or acid gat) Wait a while and you'll hear another sound cue to pick it up

https://imgur.com/Ozczdpg

Alistair's Folly- Simply start shooting the bell on top of the church with a pack a punched weapon, after that you have to shoot 5 clocks around the map.

1) In the barn above the bed - https://imgur.com/9ASCWjd
2) In the store across the counter - https://imgur.com/UAKZBG4
3) Next to barrier on the bottom floor of the saloon - https://imgur.com/OvFxICJ
4) In the Sheriffs office, left of the door - https://imgur.com/0BI6HP6
5) In the hotel above a table - https://imgur.com/5jCeDfM

You should get an indication when you do all of them, the blacksmiths door's open too when you do this revealing another perk. In spawn the Alistair is open for anyone to take!