Fast sharp prime lens for 5DIII ?

Hi team !

Hard times a while back saw the sale of my Canon 50/1.4. I often miss a small/light/fast prime for pushing sharpness/detail to the max and also making the camera lighter when on a walkabout (compared to my trusty 24-105L)....

If you could buy just ONE fast prime and wanted the sharpest picture possible, what would you buy ?...the new 40/2.8 pancake, another 50/1.4, 50/1.2L, 35/f1.4L ?

Regards
----------------------------
Formerly RichardE (heiwixivhx). Member since 2001.
Various Fuji, Canon D30, D60, 20D, 5D, 5DII, 5DIII.