COMMODITIES-Mostly down, nervously eyeing unresolved US budget

* Oil down modestly for the day, up on week and the year * Gold, copper also down on day but up on the year * Natgas has biggest year since shale gas revolution of 2007 * Soybeans best performer for 2012; coffee worst By Barani Krishnan NEW YORK, Dec 28 (Reuters) - Commodities ended broadly lower in nervous trading on Friday as traders and investors followed last-ditch attempts by U.S. politicians to resolve a fiscal crisis before the year-end. Most markets were on tente