By no means the only great Pentax lens, nor the only fun lens in my kit, but one that I have used a lot more over the last two years, not without wondering why I used it so much less before.
It appears in the PF database here:
SMC Pentax-DA 35mm F2.8 Limited Macro Reviews - DA Prime Lenses - Pentax Lens Reviews & Lens Database
I could extol the virtues of its rendering, its practicality as a standard macro, or the fun to be had in using it, but rather I would like to let a recent image do the talking: