Dun Darach
Test your tir na noggin.
Dun Darach had one of the best anti-piracy protection methods of all time. Anyone who'd sneakily copied the game to a C60 tape but ignored the instructions (members of F.A.S.T. who happen to be reading; this is not a confession) would find themselves utterly baffled. To the untrained eye, it looks like some sort of Bronze Age High Street simulator.
Of course even WITH the inlay card, Dun Darach was pretty mystifying. Here's a brief segment of the plot: "following a battle against the Conachta, Cuchulainn the Great was returning home to Muirmethne in company of his faithful charioteer, Loeg." Yes, it's fantasy names galore. It transpires that luckless Loeg was whisked away to the eponymous city by a naughty sorceress, so you (playing as Cuchulainn) must rescue him. Not too confusing, on the whole.
Baffled helplessness only sets in after the game dumps you in a street with a compass and some cash. Where to go, what to do - it's up to you. Entirely up to you, because the manual certainly isn't going to offer any handy hints. The freedom to tramp around the huge network of neatly rendered (and helpfully signposted) streets, and enter a wide assortment of shops, is absolute. Sometimes other lost souls will cross your path, and these characters may offer aid in return for incentives. But many will not.
Much like Lords of Midnight, Dun Darach abandons the player in its world and hopes they become suitably hooked. Although there are bewildering, semi-linear tasks to accomplish (apparently), finding what they are is another matter entirely. As soon as a task is accidentally stumbled upon, interest increases, but there's a nagging feeling that a few helpful pointers could have turned this intriguingly open experience into an exceptional one.