In the calculator, when you change the mode (financial, for example) to something that takes less space (basic mode, for example), the window does not shrink. This used to work, I just tried it on my Karmic computer and it worked.
By modes, I mean whatever you are changing when you go to the View (menu) > Advanced (for example).

To reproduce:
1. Open a calculator in basic mode for comparison
2. Open a second calculator and put it in programmer mode, which makes it use a bigger window
3. Open a third calculator and change the mode from programmer to basic. Notice that the window does not size back down to the size of the first calculator I opened, which is also in basic mode.
4. I take third calculator (the one I changed from programmer to basic) and compare it's size to the second calculator (which is in programmer mode), notice that the sizes are exactly the same.

This bug was originally reported as:
https://bugs.launchpad.net/ubuntu/+source/gcalctool/+bug/486359
(Video of bug attached there)