It helps to have an idea of what you may be looking for. How far do you want to go back? What era of games/software do you plan on running? Are you picky about LCD types? There are so many variables to consider.
If you want to go back to the 80's, most anything from the T3100 and T3200 lineup would be a good choice. Those machines are beautiful, extremely reliable considering their age, and are pretty good for running games made from about 1985 through 1990. However, they can be a pain in the @ss to take apart and work on, and the T3100sx and T3200sxc (but not the other models in those series) do have some capacitor related issues from what I hear.
Jumping to the 90's? Anything from the Toshiba Satellite Pro 4xx series and Tecra 5xx series are great choices. Fun, reliable, and easy to work on machines that can be used for all your DOS and Windows 9x needs. Do note that any of those that end in "cs" (example: the Tecra 500cs) do have passive matrix screens. That's not a problem for me personally, but some people complain about the slower response time of those displays, particularly those who play a lot of games with fast moving objects.