Neat 3D world constructor kit
While Virtual Reality Studio might be a long way from the concept as the makers of the forthcoming Occulus Rift see it, back in the 1990s this was cutting edge stuff that paved the way for 3D game makers. It's not a game itself, rather it is a game construction kit that is based on the technology that drove early 3D commercial releases like Castle Master and Oblivion, a system that was known as Freescape. It's all intended to be pretty accessible stuff and with a little knowledge of BASIC-style programming (if you don't know what that is, you're probably in the wrong place) and a little tinkering with things, most people will be able to have a neat 3D world of their own to wander around in next to no time at all. There's a pretty decent amount of options to play with, with pull-down menus used to create and position objects, with simple movement loops and animation added in the same way. The BASIC part of it (it's a programming language in case you're still here and didn't know) comes when you want to create puzzles and the package uses a similar system of conditions and such-like to allow you to open doors when keys are inserted, for example. Throw in the ability to add enemies which can be shot at and you're pretty much good to go. You're never going to create a true masterpiece of depth and wonder with this, but it's surprisingly flexible and powerful considering its age and there is a lot of fun to be had with simply playing around and seeing what you can come up with. The follow up, Virtual Reality Studio 2.0 is actually probably the better bet as it includes a bunch more options but this is a good place to start if you're interested in old-school games design.