I may be a few miles away, but if you're in Seattle, you should check out Lost Lake Cafe. It opened a little over a year ago, so maybe you've already been there, but I just discovered it a few weeks before we left and it is easily my favorite 24hr. spot in the city.
The food is classic diner/cafe fare done well, I'm a fan of the pie and they have some great specialty cocktails, too.
On top of the great food, what makes this WAY better than hitting up a Denny's at 2 am is the decor. It's a cross between a 50's diner and a hunting lodge, sort of a retro getaway in the middle of Capitol Hill. Check it out. It's always open.
Teresa, they have waffles. We have to go when I get back!
Also, they have a happy hour.