I developped a small thing last year when i was building a patch that would do the work of a mixing console. What i was trying to achieve was to make it as handy as possible so that i could mix my songs live. In particular, i needed a control that could move both the volume and the pan sliders of one track at the same time. Since i have only one mouse, i needed something that could control the pan according to the X-axis of the mouse, and the volume according to the moves along the Y-axis.
I have called it [wheel] (don't ask me why, i can't remember). Just open it, the workings are pretty straightforward. This certainly is no big deal for most Pd users, but i believe it can be useful to some.