The most unpretentious SLR lens is, in my opinion, the "Nifty Fifty."
Most of the major SLR manufacturers have a relatively cheap, great quality 50mm lens. Canon has the EF 50mm f1.8 for about $100, and Nikon has the similar Nikkor 50mm f1.8D for about $120, and the Sony SAL-50F18 for $150 These are the Nifty Fifty lenses that everyone should own!
(There must be others that are available, but this is the list I compiled from B and H Photo.)
Submit your best photos with your Nifty Fifty.