A couple of my favs:

The Five Spot, up on Queen Anne - albiet not quite downtown, but if you work downtown and have a car it's a 5-8 minute drive tops. In terms of in the immediate towntown area...

Rama on Post - Thai food, on 80 Post Ave, basically 1 block south of WaMu tower and two.5 blocks down.

Wild Ginger - As suggested always good for some pan-asian.

Gretchens (sp?) - In Benaroya Hall it's a great quick hot-turkey sandwhich place. Served with BBQ sauce. Also have various salads and special soups.

The Brooklyn - Can't go wrong there, located on the 2nd ave side at the bottom of the WaMu tower. Tons of types of Oysters as well as great Northwestern food.

Nikko's - As mentioned above, by far one of the best deals around in terms of Sushi. All ya can eat - awesome sushi and $14.95. Better for groups in terms of sushi eating.