Much has been talked about the various ultra wide angle lens from PENTAX and Sigma . However if one needs a quick and varsatile lens, i think the much neglected DA 16 - 50 f/2.8 is highly capable for the task. For a start the focal length of 16mm gives a film equivalent of 24mm , which is considered wide . this angle already gives a good perspective in most situations . Then there is the 50mm , giving a good 75mm, which is suitable for portrait, with good oof at f/2.8. Below are some examples of what this lens is capable. Other Pentaxians with this lens are free to contribute their photos taken with this lens in this thread.
IMGP8462 by maverick_h, on Flickr
IMGP8462 by maverick_h, on Flickr