Halloween is my favorite holiday, mostly because I love zombies. I also love a good haunted house, and it took me a couple of years to find a good one in Seattle.
My favorite haunted house in Seattle is KUBE 93 FM's Haunted House at the old Georgetown Morgue in SODO. I went last year and I was properly frightened from the experience. I don't want to give away too many details, but there were rooms that grossed me out, rooms that gave me vertigo, and rooms that startled me so much that I screamed out loud. Also, it's at an old morgue. An old morgue! So creepy.
Now, I am kind of a wimp when it comes to being scared so I scare pretty easily, but this was not a kiddie haunted house by any means. Casper the Friendly Ghost does not live in this haunted house. Although, it's not going to scar children for life, either, like, if you took your kids to the movies to see The Godfather or The Black Hole.
My advice is get there about 20 or 30 minutes before they open so you don't have to wait in line forever. Or, there is the option to pay $10 more per person to get in the VIP speed line, which means you get to cut in front of the line. You can buy tickets online, and view the haunted house schedule online.