Favourite so far is the Planar Sphere, but the Bard's one sounds interesting. Paladins have interesting subquests, but their stronghold leaves a lot to be desired.
Spoiler for Planar Sphere:
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Heh, the main quests for the Planar Sphere is the training of three apprentices. If you are cold-hearted, you can make them forge powerful items for you, but at the expense of their lifes.
Should they survive, there will be a graduation ceremony.
After some time after that, you will be given a quest to assassinate a magic-hater, and after all this, one of your apprentice will return to 'work' for you. He will make a batch of potions for you once a week.
The Golem is useless once you get the Planar Sphere.
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If not a Sorcerer, then a Paladin.
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Baldur's Gate Item Mart