This is one of my favorites. You play as one of four characters who stole a gem from a dragon, and then lost it. You want to get it back. You can also be the dragon.
There is the adventurer, who plays as a Zork-type PC, gathering items and chatting with guards; the thief, who remains hidden and has special tools; the wizard, who can use spells; and the royal, who can command everyone and has an entourage. The dragon does, you know, dragon things.
The game is hard, but you can switch between characters at any time, and one character can see things that will help another.
Location and object descriptions are different with each character, giving the game a really varied feel.
By far, this game is the closest to a straight-up D&D type setting, which I love.