Sushi Lounge [132 St. Mark's Place (at Ave. A) 212-598-1188]
All sushi is 50% off all day. And it's pretty good too. Also, they have a fantastic happy hour deal on drinks from 10 pm to 1 am every night ($6.25 pitchers of Kirin!). I had the Zaru Soba, which was decent, but not exceptional. All in all, however, this is a solid option for downtown sushi and a good way to conserve funds if you are going drinking in the area.