It just occurred to me this afternoon that Window's standard calculator application has a "GUI blooper". Can you spot it? Hint: It has something to do with multiplication.
The blooper is the use of the asterisk (*) symbol for multiplication instead of the traditional x symbol. Look at any calculator, physical or virtual, and you'll always see the x symbol used. My guess is very few non-technical people know * stands for multiplication, and the only way they figure it out is by process of elimination.
So why does Windows use *? Practically every programming language out there uses * for multiplying, thanks to the yahoos who forgot (chose not) to include a multiplication symbol in ASCII. So to the programmers who wrote the Windows calculator, using * seemed only natural. I just wonder how this got past their usability experts.
Update on 4/28/08:
Dustin makes a good point in the comments below that Microsoft was likely just mapping the symbols from the number pad. Consistency is a key to good UI design. But, I think the carrying the limitation of the keyboard into the GUI isn't the best decision. It would be like only allowing the OS to have 12 major functions because there are only 12 function (F) keys on the keyboard.