Baldur's Gate had some incredibly bizarre things characters would say.
"You're a queer fellow." I am? What did I do?
"Stop touching me!" in an incredibly high pitched, whiny voice. The first time I heard that it actually scared me.
"Squeaky wheel get's the kick!" What the hell does that mean?
"My old girl's as clean as an elven arse." That image is just a bit disturbing.
Then there's Morrowind's "N'wah!" and "S'wit!" Perhaps the two most ridiculous sounding insults I've heard.
I'm also a fan of Oblivion's "This is the part where you fall down and bleed to death!" and "Why... won't... you... die!?"
And to be honest, I actually liked the "I will be your doom!" I'm not sure why. I guess it just sounds funny.
Anything said by the player character in Neverwinter Nights 2. Out of the twenty-some choices for a voice, there was only one that was even slightly tolerable.