What is this plant?

I think your plant is Black Nightshade. I wouldn't completely rule out the possibility it is Deadly Nightshade, but I'd say 'Black' is more likely, due to the way the berries are arranged in a cluster. Very toxic. It doesn't have any attractiveness as such, or any ornamental value. The plant just makes leaves and rather poisonous berries, so I would recommend destroying it. Symptoms if ingested are: nausea, vomiting, profuse diarrhoea and colic, headache and respiratory depression, cold clammy skin or fever, and delirium with slow or fast pulse. But deaths are rare.

Thank you Jonathan....I had no idea!

It is indeed Black Nightshade.