This isn't a "rebate" as such, but starting July 1st, residents of British Columbia and Ontario will not need to pay sales tax on some purchases in Washington state.
http://www.cbc.ca/canada/british-col...exemption.html
This is in addition to an already lengthy list of exempted states and territories. A full list is available here.
http://dor.wa.gov/Content/FindTaxesA...s/default.aspx
Unfortunately, the exemption does not apply to food and lodging.