I once had beef served with "mashed pears" (think mashed potatoes but made of pears instead) and a sweet raisin and cinnamon sauce. It pretty much sucked, and the beef was terribly made. Too bad the menu was decided in advance.
A combination I do like is blueberry cake with chocolate ice cream.

Not that strange though. I once saw a recipe on blue cheese ice cream. I like both, but can't imagine them both together.
Blue cheese on gingerbread bisquits is a rather well known, great but slightly odd combination. Yum.
