Top Picks: Marukame Udon (Udon, Cheap Eats, Lunch/Dinner, Waikiki)
Ultimate comfort food. This was one of the best meals we had on our trip, situated smack in the middle of Waikiki, super cheap and super fun experience. If you walk the streets of Waikiki you’ll notice a snaking line outside here at lunch and dinnertime, hop on. 
The line is mixed with tourists, locals, and lots of Japanese people. You can longingly watch people on the inside of the restaurant eating their noodles, and when you are almost there you may take note of a display case explaining some of the soups. The food is so worth the wait, I have never had such mouthwatering udon! When you enter the threshold you will see employees taking the steps to prepare fresh udon. 
This is a cafeteria style restaurant so prepare you order in your head and recite it to a friendly English speaking man at the counter. Take your tray and watch him scoop heaping amounts of soup, noodles, and goodies in the bowl (sizes come in regular or large, and regular is extremely filling!). Jeff got the Niku which has sweet beef and I got the Ontama with a soft boiled egg. 
Walk down the line to the tempura station and look at the variety before you ranging from the typical shrimp to all sorts of interesting veggies. 
We tried onion, asparagus, and super tasty mushroom. Make your way to the condiments section and fill up a soda, their unsweetened green tea is a great option. Somehow, magically, although you wait in line for however long you will find a seat open. You can use a big soup spoon, a fork, or chopsticks. I tried with the big soup spoon, and then switched to the chopsticks. They were slippery and I was having difficulty even though I am an adept chopstick user. I momentarily looked out the window and saw an oriental couple motioning to me how to best eat the soup, and that is quickly and close to the mouth! I laughed inside, they laughed outside, and I had no more trouble eating. I have had udon a few times prior and always found it nondescript, and even downright unpleasant at times. I can’t describe how savory and perfect this soup was. This is truly a must try for lunch or a very cheap dinner (two of us, $20, in WAIKIKI!) when in Oahu.