If a device you are using (whether it's a pedal, synth, or rack-mount processor) has an “Expression Pedal” input, always experiment with it! It can transform a one-dimensional effect into a very useful device.
Many older analog devices let you choose only one parameter to control, but most modern devices with a digital brain will let you set any and all parameters to change with a single pedal sweep. The possibilities are endless for studio or live applications.
There are also some new devices out that will let you control three devices with one pedal:
Mission Expressionator Multi-Expression Controller Pedal
This little guy will not only let you control three devices with one pedal, it will let you control two or all three at the same time, and also choose a swell type.