Last night I ate at the Blue Marlin on Sawtelle across from Nijiya market. Normally I am not impressed with restaurant pasta - often overpriced and bland. Hence, I seldom order it out. But I go to Blue Marlin, a self-described "Japanese Bistro" solely to eat the pasta - they really do it well given that it only costs about $6 or $7. (I recommend side-stepping the more expensive fish dishes)
The penne arrabiatta is perfectly al dente and spicy, very garlicky and somewhat sweet.
The first and cheapest entree is also really good, just spaghetti with red pepper and LOTS of garlic.
Also good and somewhat unusual is the Oba- the spaghetti with plum sauce and Shiso. The first time I ordered it I found it strange but it grew on me. Later I found myself craving it and have been a fan ever since.
And I have heard that the Mintaiko pasta (a type of fish roe) is fantastic. Haven't tried it though.
Oh - the carrot-miso salad dressing is also good although our salad last night was sandy.
If you're in the neighborhood, hungry and don't want to spend a lot of money, give it a try.