In the right hands, ultra wide-angle lenses can produce awesome images. They can also be awsomely expensive, especially the ones made by the same company that made your camera. If this rings true for you, take a look at Vivitar's Series 1 13mm/f2.8 Aspheric Super Wide lens.
Made in Pentax K, Canon EOS, Nikon and Sony/Minolta AF lens mounts, the manual-focus Vivitar Series 1 13mm f/2.8 Aspheric Ultra Wide is designed to work with film-based SLRs as well as APS-C format and full-frame DSLRs. With an angle-of-view of 113.8° when used on a full-frame (D)SLR (and approximately 99° with an APS-C format DSLR), the Vivitar 13mm f/2.8 Aspheric can produce truly dramatic landscapes, architectural and interior photographs, though it should be used rather judiciously for portraiture.
With a close-focusing distance of 12" (30.5cm), the Vivitar Series 1 13mm f/2.8 Aspheric can capture dramatically dynamic close-ups of products and any number of other subject matter.
And though it contains a hefty number of elements—16 in 13 groups—it only measures 3.2" (81mm) long by 2.9" (74mm) wide, with a weight of 15.3 oz (434 g) making it an easy lens to pack away in your bag for traveling and day tripping.