Rokurinsha's tsukemen is probably the most popular in Tokyo right now. It's incredibly delicious, but so was every other tsukemen shop we went to. The difference, at least from my experience, was that the noodles were more firm. So firm, that flail wildly like thick ropes, slapping your face as you slurp them. Luckily, they provide bibs.

If you've never tried tsukemen, it's a dipping ramen. A pretty foreign concept for even hardcore ramen eaters, but if you eat it as it was meant, you'll surely enjoy it. 

Traditionally, the noodles are served cold along-side a molten hot, salty, reduced tonkotsu broth with fish powder. The hot broth takes the chill off the noodle, and the cold noodles cause the broth to congeal to noodles. You don't pour the broth over the noodles, rather it's meant to be dipped per mouthful.