AH Halloween my favorite!
I suppose it doesn't quite qualify as DIY because I have a certification in special effects make up and we did this as a class project but building haunted houses was a passion of mine.
We always managed to get a building donated for the 2 months it took. Usually a building in a mall was available.
There would usually be 12 - 15 students helping out and a core group of 6 or so.
I guess my favorites were a gypsy fortuneteller in a bayou cabin.
She sat at a table telling the ill fortune of a woman about a murder that she had been involved in where the head was never found. There was a guy-wire of monofilament that ran from an obscured little curtain high in a corner straight toward the door where the audience would be standing.
On cue the actors stepped on a button releasing a severed head that would come flying out toward the audience. We had 3 people pee their pants including a guy in his 20s that had been outside telling his friends that nothing we could do could scare him.
The next one was a bit odd to me. we had a "tunnel" that the people had to walk through that was lined with vines and moss. we had tiny fiber optic threads that blew around on the ceiling and stereo speakers that played the sound of mosquitoes. Using a sound board we would change the sound from side to side and front to back, using a dozen little speakers. We also had a tiny computer fan blowing in the odor of a swamp.
This was right at the front as they came in and just after the gypsy cabin.
Around 1 out of 5 chickened out before they would enter the tunnel. Even though they thought they would be loosing their entry ticket charge, but if they didn't make past that we always gave the money back.
There were so may others I can't even begin to list.
We / I had such great fun doing all of this and would come from work at 6 and usually work till 2am every day, but it was so worth the effort.