Tomolives are small pickled green tomatoes that taste like a cross between a caper berry and a dill pickle. They're available at some grocery stores or online at zabars.com or amazon.com.
Fill a martini glass and a shaker with ice. Add gin or vodka, vermouth, and brine to shaker. Shake vigorously 30 seconds. Remove ice from glass. Place a few tomolives in bottom; strain in martini.