For the relatively new-to-me Minolta X-570, it's the nMD 35/1.8.
On the mono-converted rII, it's the 7Artisans 35/1.4 vIII.
On the UT modded rII, it's the ZM Biogon 35/2.
On the a6700, it's the Sony 70-200GII.
On the a1, it's the 300GM.
On the FX3, it's the Zony A-mount 24/2.
And on the Actus it's the Rodenstock 100/4.
So I guess it just depends on which camera I'm holding when I croak.
I'm sure that I'd change my mind one day but I've had the Leica summicron-r 180/2.0 since the mid 1990s, bought it new, and still can't see myself parting with it. But it is getting heavier, or gravity is changing, I definitely can't be getting older... right.
Aside from that, I've not seen a better fast 50 than the Sony 50/1.2 and I certainly can't imagine ever parting with it.
I went through this exercise once when I had to sell off most of my large format gear due to a lengthy medical crisis. The last lens I parted with was a dearly beloved Kodak 135mm Wide Field Ektar. What a fantastic lens. Fast forward 20+ years or so and I've finally found its digital sibling, Voigtlander 40mm f1.2 Nokton. If the time ever came again when I needed to divest myself of my gear, that will surely be the last lens to go.
Cold dead hands make it tough to shoot. I have been there when it is 5 degrees, they are stiff and sometimes I can't even tell if I hit the shutter button.
