For the strange but cool department:

Flash: 99 Rooms
99 Rooms. Enter at your own risk. (I haven't wandered too deeply, yet.) It's easy to waste time here! [#!/usr/bin/girl]

It's not a game. But it is interactive. This is one of those things that I think flash is really cool for. This reminds me of some of the early stuff I remember people doing with Quicktime ages ago.