M43 shooter - the Olympus 20mm f1.4.
Weather sealed, great focal length, balances well on my medium sized bodies, and got so much crap because of purple fringing on early reviews that I was able to buy it cheaper new than used. Folks are starting to catch on and it's becoming more popular. Such a nice and compact travel lens.
I never tried the 20mm 1.7 but I've seen image samples and think it's fantastic for what it is. The biggest thing for me was the weather sealing, I wanted that and adored the Oly 25 1.8, but thought the Oly 25 1.2 was too big for EDC and backpack travel. The 20mm 1.4 was a nice compromise and it sits nicely on my EM5.3. It's been by far my favorite lens, and since m43 lenses are cheap, I've owned and sold a good amount.
I have the 12-40 2.8, but I've been seriously considering selling it for the 8-25 F4 for some time now.
I've been looking at the PL 25 1.4 II lately. My only worry is how the PL weather sealing holds up on the Oly bodies.