Vivitar made a 19 mm f3.8 which is/was inexpensive and pretty good. Reasonably low distortion, and at mid apertures pretty sharp. The lens is nicely made, all metal, and feels good. Plus, it uses 62mm filters, as opposed to the 77mm monsters that Newt_on_Swings mentions in his post about the Vivitar 19-35mm.

While I've had this lens several years I haven't used it all that much. As others have noted it "sees" so much that framing must be careful to avoid junk in the pic, and the inevitable convergance of vertical and horizontal planes if the film plane isn't lined up with the subject can be alarming...unless that's the effect you're after!