While there's some waffling on the "fast 50" variant as the FA 50/1.4 being a must have -- and I'm one of them now because of not having the greatest luck with AF wide or near wide open -- I do not waffle on the Pentax-A 50/1.4 or Pentax-A 50/1.7 MF lenses for $100 or well under given the luck I have had manually focusing wide or near wide open.
With that said, I won't ever give-up my FA 50/1.4.
I want to also say "and the Voigtlander 125/2.5" but that would be like salt in a wound for those without one already.
So any other similar focal length & aperture Macro lens that is also known to work great @ infinity... most all the Macro lenses around 90mm-135mm are insanely high resolution, most (perhaps moreso the MF ones?) with few lens artifacts or very well controlled, & a must have.
Given the cropped sensor, some wide angle is a must have, but I'm not about to say it needs to be the one I have, the 12-24/4. So a non-answer on that other than "one of them".