Top Squished Bugs

Some uses for this page:
 * The Release Checklist can be a little soul destroying as there are always more bugs to hunt down and remove. New problems are discovered and new technology arrives that breaks code which once worked.  A list of bugs from the past which we have fixed helps to counteract the sinking feeling when looking at bugs remaining to fix.
 * Bugs that have reached a 'closed' status should not just be forgotten about. Understanding their causes helps us to test for, find and fix bugs which have similar causes.

Edit Hint: Some more text about each of these bugs would be very welcome.