Your favorite lenses for Pentax cameras

[zephyrsky]

I’ve been patiently saving my yen to expand my lens collection, and while I’m not looking for recommendations until I narrow down what I’m looking for, I’d love to hear your personal opinions. As a relative novice, I often see similar threads for Nikon and Canon users, so why not give Pentax users a voice?

What are your favorite Pentax mount lenses? Similarly, what lenses do you feel are the best to use in which situations/for which scenes?
Pentax-branded, third-party and other brands, zooms, primes, wide, macro, budget, expensive… Anything is okay!

[mattdm]

I love my DA 40mm f/2.8 Limited and DA 70mm f/2.4 Limited. They are a pleasure to use and produce great results.

I wasn't so keen on the DA 21mm (finding the 35mm equivalent focal length awkward, even though it's a "classic"), but I'm sorely tempted by the DA 15mm.

[heatherwb]

Before switching to Canon, I used Pentax, so I'll share with you my favorites...

Extra WA: DA12-24/4
General walkaround: Sigma 17-70/2.8-4.5. This one has been updated, but if you can get a hold of a sharp used copy of the first version, it's a great lens. If you want to try your hand at close-up, it also focuses at 1:2.3 macro ratio at 70mm.
Telezoom: DA 55-300 Go ahead and pay the price for it, as it's definitely better than it's Sigma and Tamron counterparts (70-300). It was a sharp lens and a joy to use whenever I needed tele.

True macro: DFA100/2.8. Don't let the plasticky build turn you off--this is an excellent lens.
Somewhat "normal" prime: FA43/1.9--this is one sharp lens and worth every penny if you've got the cash for it.

Older manual focus lenses: A50/2--can be had for $50, sometimes less--a really cheap way to get started in primes. If you go this route, make sure that the aperture ring is set on "A" and it'll meter just like the newer AF lenses--the only thing that's missing is the AF.
M28/3.5--you'd better be wearing eye protection when looking at pics made with this lens--it's that sharp!
K55/1.8--love the bokeh on this thing...

HTH,
Heather