Anomen has a really nice shield, plus 2, fire and ice resistance, and only he and my main character, a cavalier, can use it. Korgan and Korgan cant use it. Why can a Cavalier and a Fighter/Cleric use it, but not a Range or a Fighter?

It might be a unique item. I'm surprised that it doesn't mention it in the text but if it is your char shouldn't be able to use it. If you look at all the unique weapons in the game (Yoshimo's katana, Valygar's armor, Jan's technoshit) only those NPCs can use them.

The shield isn't tied to Anomen. My Paladin can wear it. However, my cleric can't even though she otherwise can wear all kinds of shields.

BR

Axel