Green onion and sesame oil are both a MUST for me! I also add a little vinegar to the noodles when I add them to the boiling water. I think this improves their texture and makes them bouncier and springier. I also like to add any leftover veggies I have in the fridge, black pepper, shichimi togarashi, and sometimes sesame seeds and a little garlic powder because I love garlic.