Sigma just announced the world's first f/1.8 constant aperture zoom lens, the “Sigma 18-35mm f/1.8 DC HSM Art.”
This extreme wide aperture, standard zoom-lens for DSLR camera's with APS-C (1.5~1.6x crop) sized sensors. On such cameras it has a 35mm format focal range equivalent of 27mm – 52.5mm (depth of field equivalent at f/1.8: ±f/2.7).
The fact that Sigma placed this lens in their “Art” lens series is an indication of the high quality we may expect of the lens. As of now, no exact release date nor indication of price (likely > $/€ 1000) has been given by Sigma.
For more information, see the Sigma product page.