Konami's Playstation DDR Hand Controller (circa 2000)
This was a home controller for use in your hand designed by Konami and sold in 2000. Although DDR could be played on controller perfectly fine for 1P mode, it was a bit of a hassle to play SOLO (6-panel) or double (8-panel) since that required a combination of the L/R buttons and/or a second controller (though there are people quite comfortable with the 2-controller setup).
Okay, the button layout is obviously designed to mimic a DDR Stage for your fingers...well, kind of. It puts two 6-panel (SOLO) stages side by side. The button layout is as follows relative to a DualShock Controller:
Start/Select : As shown
1P Left : D-Pad Left
1P Down : D-Pad Down
1P Up : D-Pad Up
1P Right : D-Pad Right
1P Up-Left : L1
1P Up-Right : R1
2P Left : Square
2P Down : X
2P Up : Triangle
2P Right : Circle
2P Up-Left : L2
2P Up-Right : R2
This of course means that if you really wanted to, you could use this with other Playstation games, but the controller is a bit stiff and I can't think of too many games outside of maybe some RPGs where it might be nice to have them on the front of the controller.
To start, it fits well in your hand, much like a regular DualShock controller. However, it does feel weird for there to be no L/R buttons, have no analog sticks, and have a slightly wider top section (it makes the top panel area more of a rectangular shape)
Once you get over that hurdle though, the buttons are actually quite stiff, even after quite a bit of use. I'm not sure if they were designed that way for more of a sense of stability but in any case, you really notice that you have to put more effort into charts that start to get fast at all. Granted, it does soften up a bit after a *lot* of use. I have considered taking it apart and lubricating the buttons on several occasions but since this controller is actually a bit difficult to find these days I didn't want to take the chance of messing it up and wrecking it or something.
For 4-panel play, I much prefer the regular DualShock. However, for practicing double play this has been a great help to me since I don't feel comfortable with the two-controller setup and it seems more natural to me since the controller is set up like a dual stage. It was also good for 6-panel play as well though I was getting used to using the L/R buttons before the SOLO/6-panel series was dropped altogether so this may be a moot point/not a selling point anymore.
If you are interested in playing double mode on controller or possibly 6-panel mode, this may be worth checking out for you, though for 4-panel play, the Dualshock works much nicer IMHO.
These controllers were not particularly expensive when they were new (2000~2500 yen) and they were under 1000 yen in the following years until they became rare. If you can find one at a used game shop or in the back streets of Akihabara, you can probably still get it for anywhere between 1000~2000 yen but if you order online through Amazon or such, you could pay as high as 3500~4000 yen.