Pepper spray is legal in all of washington.
I have not found anything that restricts a baton or taser but it could be there somewhere.
Also you can carry a knife as long as it is not a "dangerous knife"
Exerpt from SMC 12 definitions
Code:A. "Dangerous knife" means any fixed-blade knife and any other knife having a blade more than three and one-half inches (3 1/2") in length.