I have dabbled around with a few others, but I am very happy with the pk-5, which I use for live performance several times monthly. For the price, I would say the pk-5 is the most sturdy and legitimate pedal controller on the market. The Moog Taurus 3 of course are another very good option (and those have their own sounds on board in addition to being able to act as a midi controller), but the price is not really in the same ballpark as the pk-5. So it depends what you're looking for.
This thread also has some other options, including a lot of DIY alternatives. Bass Pedal (Taurus, Roland, MIDI, etc) Club?