I am doing a run through with a Chaotic Neutral Charname right now doing some deliberately bizarre things to reflect the alignment and her extremely low wisdom score and just got my first wisdom tome. Part of the run is also going through without any cleric or druid in the party (Charname, Imoen, Monty, Xzar and Edwin). I looked at Edwin and Imoen and determined that the 3 tomes of wisdom were useless on them since they couldn't get to the 18 wisdom needed to make that useful in BG2 for the wish spells. Then I noticed that Xzar has a 16 wisdom, gave him the tome, and dualed him to a cleric. This gimps my party but should be entertaining.
Hopefully this topic isn't duplicating one already out there, but I thought it might be useful for people to have a discussion on which NPCs can dual class. I think everyone knows Imoen can dual to mage.
Shar-Teel makes a great thief.
Branwen can dual to thief with the dex tome.
Safana can dual to mage with the int tome.
Dynaheir can go cleric with two wisdom tomes (thanks sarevok57).
Any other NPCs that can dual?