What is your favorite restaurant in Chicago that does NOT take reservations?

Fellow Chicagoans - help a guy out by naming your favorite restaurant in Chicago that does NOT take reservations. Your suggestions may influence an impromptu Valentine's Day dinner.

I'll get the creative crowd source juices flowing by naming the only two "no reservation" restaurants that I know of - Au Cheval and High Five Ramen (both Hogsalt).

Thank you for your expertise in advance