West Seattle light rail
In about a decade, West Seattle is scheduled to open its segment of Link Light Rail from Downtown Seattle to the California and Alaska Junction. Even now, the Junction is expensive real estate. The West Seattle Junction is full of expensive apartments. Elevated light rail would put a train in everyone's bedroom. The Junction is not an appropriate place for an elevated railroad. West Seattle is an appropriate place for a tunnel.
However, I don't think that Sound Transit or King County or even Seattle should have to pay for West Seattle's tunnel. Technically, the tunnel is an amenity for West Seattle. The tunnel should be paid for by West Seattle. If West Seattle can't find a way to pay for its own tunnel, it must not have been that important in the first place