Climbing Nightshade (Solanum dulcamara) is a non-native perennial climber who produces red fruit that look temptingly like small grape tomatoes and which can persist from the growing season right into winter. This species is closely related to edible cultivated tomatoes, but forager Samuel Thayer reports that the fruits of Climbing Nightshade "are somewhat poisonous" (Nature's Garden, p. 379). I've seen this climber weave her way up sections of metal fencing, including a fence in my former Massachusetts backyard. This fruit-filled plant in this photo is living among large boulders along Fortune's Rocks Road in Biddeford, Maine.
Note: This plant is also called Deadly Nightshade or Bittersweet Nightshade (I reserve the name bittersweet for the unrelated vines of the genus Celastrus).