Bonus spells for a cleric/druid plus a saving throw bonus. Also it affects how high lore you have. It may have an impact on some conversations but I really don't know.
Wisdom has no effect on saving throws. (The manual says it does, but that feature was not implemented in the final version of the game.) Wisdom affects the number of spells a Cleric or Druid can cast (there are tables in the manual), and it affects the outcome of a Wish spell. When it comes to the dialogues, I can only think of one place where Wisdom is checked (the Spectator Beholder), but there might be a few other places.
