There are a few games I always wanted to learn how to play but never got around to it. One is a game called lifeforce. It has a strange concept and starts out with some really cool music. And you have to capture thingies. But I think every time I got around to getting the instructions I never got around to playing the game with them in my hand.
Another game I have never really learned how to play is Eastern Front. My biggest complaint about war sims is they are too big. At least that one is on a smaller scale. Actually I thought it was on a smaller scale until I got a hold of the instructions :) Makes me really enjoy a single screen combat sim like V.C.
Both the Eidolon and Koronis Rift can be messed around in but again I never really got too deeply into either.
And there is this activision game called Pastfinder that looks so cool for it's style. But I keep loosing the instructions
One game I keep forgetting how to play is E.T. It's a much better game than the Atari 2600 version. I even have the instructions. :)