1)
The Seoul House (in the circuit city / burlington shopping center) has $1 sushi nights. Also it's just a really nice place in general.
2) There used to be a really good place Teriyaki/sushi place in Vienna in the Macgruder's/Rexall shopping center on Maple Ave. Park in that lot and then walk down Maple and it will be on your right. I don't know whether's it's actually there anymore. They have an unbeatable lunch special. Here's a lame map.
......Foster'sI_____________________Rexall____MaGruders_
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Sushi_______
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