What is the best toy for newborn?

Squeaky toy; rattle. Newborns don't play with toys, so the best toy for a newborn would be a toy that mom or dad can play with to try to catch the newborn's attention.
None. Newborns (0-2months) don't need any toys. You are the best stimulation. If you desire mobiles on the bed that are brightly colored would be the only thing that would be fun. Most newborns sleep up to 21 hours a day and when awake are feeding and wanting interaction with you...Which is awesome.
None. Newborns feed, sleep, and want to be held. They do not need toys. When they are awake and alert, the best "toys" are mom and dad. Hearing soft voices, watching your faces, and being held, walked and rocked are the best ways for a newborn to be "soothed".