In Shadows you would have had the option to sell a baby you kept as part of a questline into slavery, but it was Dummied Out.
Hordes has many options dummied out for usages of the True Names of characters, likely due to the Video Game Cruelty Potential it offered, commanding people against their will to do things for you. However, a truly hilarious ending was cut as part of this: commanding Mephistopheles to serve you as your chambermaid.
Keep Circulating the Tapes: For a while, there was no official support or distribution for some premium modules such as Infinite Dungeons, until GOG released most in their Complete Edition.
Screwed by the Lawyers: Because of the change between publishers, from Interplay to Atari, changes had to be made in the storyline so that characters from Baldur's Gate wouldn't carry to Neverwinter Nights.
Trope Namer: BioWare homebrewed several spells for the series, including a pair of spells called Isaac's lesser missile storm and greater missile storm. In conjunction with the original magic missile, they name Magic Missile Storm.