Pacific anenome is a cute little perennial that has a lot of versatility in the garden, largely because it manages to pop up in a huge variety of habitats on the landscape. You can find it in open woods, in meadows, in alpine clearings, and on dry rocky ridges and slopes (and probably lots of other places too). My plants are grown from seed gathered in open cottonwood/ponderosa forest in the valley bottom, so they are perfectly adapted to lowland life. 
 
Pacific anemone has one or two buttercup-sized white (sometimes pink) flowers on each slender stem, and gorgeous finely-dissected leaves. Like all anemones that I know, it makes a neat looking oblong seedhead that produces adorable fuzzy seeds. It does tend to go dormant when it's super hot, so don't panic if it wastes away in August or September; it'll be back, forming loose clumps over time that can be divided.
 
This plant is tidy and well-behaved, perfect for your rock garden or the front of your garden border. It likes full sun to part shade, and while it is drought tolerant it definitely seems to appreciate some extra moisture in the summer. I think this species would go very well with wilcox or alberta penstemon and any of the pussytoes, but it will be a good neighbor to pretty much anything that won't run it over. 
 
last image credit: Matt Lavin from Bozeman, Montana, USA, CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons