Ed,
Yes, almost any game can be driven by a touchscreen, but there are some games that take to it better then others. Likewise, there are some games actually designed for touchscreens, and work better with them. World of Goo is an example of the former; Crayon Physics is an example of the later. However. both of these are commercial games. I am looking for the obscure, unknown, forgotten, niche, or hidden gems that are routinely overlooked by most people.
Also, if you noticed, I'm not looking for MAME games. I know all about touchmaster, and some of the earlier similar games; that's not what I'm looking for. I'm also not using Linux, but rather Windows. That is a point I failed to make clear previously, and for that I apologize. However, everything else I listed still stands: I'm looking for freeware games that work well with a touchscreen alone, or are designed from the ground up to use a touchscreen - and a single touch screen at that, not a multitouch one. Many people on here have built their own touchscreen arcade units, and most use far more then just commercial products to do so.