I'm a Lightweaver and my favorite investiture on Scadrial is Feruchemy. Also, what is the thing with cookies? I am confused...
I think I've read all of the ones that are published except the 2nd White Sand, The Wheel of Time books he wrote, and a couple short stories. As for my favorite character(s), I love Renarin, Vivenna, and Shai.
It's so hard to pick just one! But the two I find myself coming back to the most are The Emperor's Soul and Words of Radiance.
Probably Forging on Sel. But I really like the one in The Stormlight Archive too.