For starts, I use my K-3 for action, and my K-1 for landscape.
My wife Tess however shoots her K-5. Her combination of choice is currently the DA 16-85 but she took a few with the DA 55-300 PLM as well.
My choice for our last trip was the K-1 was the DA 28-105 and a second hand Sigma 24 2.8 macro.
A few images....
K-1 and DFA 28-105
And the Sigma 24mm
And one landscape taken with the DA 55-300 PLM
These lenses make a nice lightweight, easily portable kit that can do about anything.
Pentax doesn't give you a lot of choice, but what they make is top quality. You learn to live with what they have, and when you have lenses like the DA 16-85 and DFA 28-105, you might think about different focal lengths, but not about the quality of the glass in the offered focal lengths.