The makers of Viagra are pulling all the way out of Williamsburg. Global pharmaceutical giant Pfizer — which operated in South Williamsburg from 1849 until closing in 2007 — has listed its last three parcels on Harrison Avenue near Gerry Street and Wallabout Street. The price? “Negotiable,” according to the sales listing. The properties represent the last trace of the company’s 162 years in Brooklyn — a legacy that includes reducing cholesterol and enhancing erections — and the proposed sale is a blow to neighborhood residents and housing groups who hoped to develop below-market-rate housing there.