Control panels for various hardware. I could think of many uses in music synthesizers for example where access to many parameters for quick modification during live performance can make the difference.
I have a Roland/Boss GT-100 guitar processor (a big pedal board), which features 8 programmable/assignable open-ended rotary knobs (open ended as they can just be kept rotating without hitting some kind of stop). It would be great to be able to _feel_ hitting certain settings when brushing them with my foot, without having to look at all.
As a musician, I think the introduction of haptics to electric/electronic instruments allows you to move in unexplored aural directions, which is sometimes very musical.
On a related music/audio note, I recently came across videos of the teenage engineering TP-7 which looks like a really cool application of similar haptic feedback concepts. Unfortunately it's out of the price range where I can justify picking one up just to tinker around with it, so I've only seen videos of it so far.
