As someone guilty of pronouncing names completely wrong, I want to hear some of you guys's.
I'll start.
I thought Alethi was Alenthi and pronounced it as such.
I pronounced Gavilar as Gavinar
Don't get me started with Elhokar, I don't remember what I did but it was wrong. I think Elk-o-har?
Minor but pronouncing Jasnah as jah-snah instead of ya-snah.
I don't really pronounce Urithiru at all. I've decided to not even try.
Cephandrius as Cephardius.
Chasmfiend as chasmfield, I really don't know why.
Not specifically cosmere but duralumin as dur-ay-lee-um.
There's probably more I can't think of off the top of my head. What about you guys?