I'd have to say my first solo: With an Elven Diviner, playing through the whole saga. After dying tens of thousands of times to the wolf by the area of the batte, I figured, "Ah hell. Unless I see an ogre drop a spell scroll, that 86 gold pieces on his body is *not* worth it."
Baldurs Gate 2 came, and had me changing my spell list MAJORLY. Spells that I had previously thought useless were becoming lifesavers, and previously fun spells were completely useless.
And then came ToB... Area effect spells, art thou the mage's lover?