If you're in or from the New England area, Trail of Terror in Wallingford, CT is one of the best sort of hidden gems you'll find.
Superbly executed haunted trail that is always evolving and changing year to year, executed super, super well with keen talent for multiple methods of scaring, amazingly populated and decorated mini worlds that will take you up and down and around a tightly packed woods. Not only a great bargain price point ($25 a ticket is an absolute steal for the amount of scenes, actors and quality you will get), especially compared to some of the other local higher notoriety events. Conga lines are unattractive inevitability of the medium but Trail of Terror go out of their way to maximize the guest experience as much as possible in making a better, singular experience. They go out of their way to notice how big your group is, only let smaller groups of around 6-8 go through at a time, have several slow down points that can help pulsing and there's even a Mid-Way where groups in total are pulsed with space. Even then, the trail is so well designed with its tight turns and cramped pathways that it's very easy to feel like you're in a singular experience due to rarely feeling or actually seeing you're packed in the conga line. The trail offers a great, great mix of original ideas, archetypal Halloween haunt standards as well as a few actual IPs thrown in for good measure! It's very fun seeing a smaller scale haunt get to tackle IPs that realistically have little chance of appearing at something like HHN. This year, Trail of Terror offered up their takes on The Island of Dr. Moreau, Silent Hill, Bendy and the Ink Machine, Halloween, Silence of the Lambs, Terrifier and even a bloody, demented version The Smurf Village! Silence of the Lambs was great because it had actors in full blown nude Buffalo Bill outfits and a great gag where "Bill" would prop himself up within a doorway and force you to walk under him to escape. While I'm not the biggest fan of the films, Terrifier does provide some excellent haunt material, the scenes were super varied, you got to see some truly putrid kills and the actors got to have an absolute blast with the clown horns, waving and unending, nerve-wracking balloon rubbing. One Art actor even revealed himself behind a curtain in a scare that got both my wife and myself, which I think is a first!
Trail of Terror is the stuff of local haunt legend. I'd find it hard for anyone who loves the medium of the haunted house to be disappointed. Top notch stuff!