Patina--vinegar (white or apple cider) and salt. For small items, fill a quart yogurt container half full of vinegar, and sprinkle in about 1 tsp salt. Add any metal you want to 'age'. Seal if you touch items a lot
All natural (mostly) wood stains! A handful of pennies in vinegar will produce a beautiful pale Caribbean blue stain. A wad of steel wool will give you a rich reddish hue. A combination of tea and a metal object in vinegar will produce a black stain.