New Years Eve Downtown
It depends somewhat on your definition of "event." Nobuo at Teeter House has a special prix-fixe menu for that evening, but I don't think there will be live entertainment or anything raucous. See the menu:
Also, Steve Weiss, man-about-Downtown & a friend, has been tweeting about unpretentious NYE events Downtown using the hashtag #NewYearFreePHX
Follow him at @weissguy or just search for the hashtag to see some of his reports.