The bright berries of Stinking Iris (Iris foetidissima) glow in shady spots. They look succulent but they're toxic to humans. Birds eat them but my impression is they only do so if other food sources are scarce. Thus they add a splash of colour to the garden in the winter months. 

 Also a very common wild plant in woodland, hedgerows and scrub. One of two Irises native to the UK, the other being Yellow Flag Iris (Iris pseudacorus).