With no big theme parks in the state, Washington sure seems like an "under served" market, but it's worth keeping in mind that it's a pretty cheap flight from SEA-TAC to Southern California. What Washington does have is a surprising number of community and non-profit related amusement attractions. None of these is bigger than the State Fairgrounds in Puyallup. For two weeks a year, it entertains over a million people with a mix of permanent attractions that's greater than any other in the nation. Most famous: Classic Coaster, a wood coaster from 1935 that has the very last set of Prior and Church trains rolling in existence. It's kept in fantastic shape and is super fun (I've somehow managed to ride it?). Also - A Top Fun Typhoon coaster. Not good, but at least unique in all of North America. There's several interesting flat rides too (Huss Jump and Zierer Hexentanz for instance), a Von Roll 101, S&S Drop Tower, and a PTC Carousel at what is undoubtedly the coolest and best lineup overall of any fair in the hemisphere.
The largest permanent park in the state is Wild Waves Theme Park, operated by Premier Parks (who sold most of their operation contracts to Six Flags, except this one). There aren't any rides which one might consider a "global standout" - Timberhawk: Ride Of Prey, the park's wood coaster, was generally seen as a disappointment when it opened. Other rides and slides in the park are fairly standard production model attractions that are commonplace in the regional park universe with one possible exception. Wild Waves uses topography to its benefit by having installed a all season tubing hill - yes, snowless snowtubing is possible in the 2010s. Isn't technology incredible?
Less technologically advanced are the state's other permanent facilities. The Rides at Long Beach, WA have a set of 1960s/1970s era Fiberglass bodied Lusse bumper cars in addition to several other classic iron rides a short distance from the ocean. Remlinger Farms has a classic car ride of it's own: its Antique Car ride comes from the 1962 Seattle World's Fair. There's also train rides, a kiddie coaster, and several other attractions primarily geared for children to accompany the farm goods.
The City of Seattle is itself home to multiple attractions of note. The Seattle Great Wheel opened at Pier 57 in 2012 as the West Coast's tallest observation wheel. Standing 175 feet tall, it sure looks like a Bussink wheel (or at least from the Wheels of Excellence series he started), complete with air conditioned pods and everything. 300 feet away is Wings Over Washington, a flying theater attraction that had a lot of investment put into the theming and design of its queuing and station. It looks really fantastic for a standalone attraction of its kind.
Greater Seattle/Tacoma has a few family entertainment centers of note too. Tukwila Family Fun Center might sound like just another place with putt-putt and go-karts, but they have a strange selection of more thrilling rides like a S&S Screaming Swing installation and a small drop tower. There's also a "Driving School" attraction similar to what you would find at a Legoland park (small cars in a faux cityscape small children can drive). The Edmonds iteration of the same group's facility lacks some of the cooler and weirder stuff, but does have some 70s/80 era Italian bumper cars.
Washington, like the midwestern states detailed in previous iterations of the series, has a few fairgrounds with their own individual attractions. In the case of Washington, this means often means carousels. The Pioneer Picnic and Rodeo in Bickelton near the Oregon border in central Washington has a super rare Spillman-Herschell Carousel that is powered by a steam engine for just a few days a year during the event. Ferry County's got it's own mixed machine carousel full of rarely seen Dare, Armitage-Herschell, and Herschell-Spillman, and they were smart enough to put limitations on the sale of the carousel to prevent it ever leaving the county. The Port Townsend Wooden Boat Festival has a carousel brought in exclusively for it by the Dentzel family - it's not for adults, but the Flying Horses style menagerie carousel only runs that week specifically there as an example of their "Village Carousel" concept. While not possessing a carousel, The Evergreen County Fairgrounds does have the Western Heritage Museum offering frontiersman living museum realness.
Outside of the Seattle orbit, there's a number of smaller parks and attractions which are have carved out their own little piece of the entertainment market. Miniature World Blaine, not far from the BC border and Bellingham, has train rides with a very not-off-the-shelf miniature train. During the holiday season, they take advantage of the region's surprisingly warm temperatures to run a Christmas train with lights and displays galore. Hunter's Christmas Tree Farm in Olympia has a carousel, Super Slide, Corn Maze, and stuff like pony rides for young kids. Riverfront Park on the old 1974 Expo grounds in Spokane has a Carousel with rings (plastic, but still; RINGS!), a modern scenic skyride with fully enclosed gondolas, and a smattering of kids rides. There's also a standalone carousel in Kennewick: Gesa Carousel of Dreams: the original Silver Beach Carousel from St. Joseph Michigan.
Washington has some water parks: Great Wolf Lodge has an outpost here in Grand Mound, and there are small water parks throughout the state like Slidewaters in Lake Chelan or Surf N' Slide in Lake Moses. Birch Bay Waterslides has some old school terrain slides and a big speed slide that differentiates itself from the pack. Splashdown serves the Spokane market with modern slide tech like bowls.
Its also worth noting that there are several reasonably sized zoos in the state. Point Defiance and Woodland Park Zoos have carousels in the Seattle/Tacoma area, and the latter has animatronic dinosaurs too. The Northwest Trek Wildlife Park has tram rides and ziplining for visitors who want to get different perspectives on the animal exhibits.