Ramen Setagaya [141 First Avenue (bet. St. Mark's Pl. and 9th St.); 34-A St. Mark's Place (bet. 2nd and 3rd Aves.); 90 University Place (bet. 11th and 12th Sts.); Menu (actual menu more extensive)]
A Japanese import, this burgeoning ramen empire is for pork lovers only; vegetarians need not apply. The specialty here is the Shio Ramen. The salt-based broth is really something else and (as far as I know) it is unique among the many ramen joints popping up all over downtown. Coupled with slices of fatty pork, a soft-cooked egg, and of course, a healthy portion of chewy ramen noodles, it provides a richness of flavor not easily equaled. I highly recommend that you give it a try. I don't think it's for everyone, but if you consider yourself a noodle connoisseur, you must at least be aware of what's out there. If you're extra hungry, start with the gyoza.
The University Place location is the biggest of the three, and with multiple locations, you'll never be waiting around for two hours at Setagaya like you might at Ippudo on almost any night of the week.