I have been using HeidiSQL with please for a few years now. I would never want any other client anymore. There is just one thing that would be very convenient to have as feature that will save a lot of time writing single use queries.
I would like to propose for a way to select a single column over multiple rows and chance the value of all selected columns.
I tried to make a image to explain what i mean (with photoshop) and attached it to this post
As a addition, many text editors nowadays also have blockselect. I think this would also be a very convenient feature for the query editor.