Personally, ... I would bet that it was the Wing Commander reference in BG with the Kilrathi ship. (I think it was a Strakha, the extremely weak ship capable of Cloaking.) You double click on it, and the Kilrathi Cinematic them Plays.
![Very Happy :-D](./images/smilies/icon_e_biggrin.gif)
There is also the Blacksmith secret. I know it's by far common knowledge, but I like how they made it so very ... real, y'know? There's a lot to do in there.
There's also the secret in FoV where you find the lever behind the Stone of Cassambre, (Whatever. >__< Yeah. Kinda crazy. You can either "F3" There via the cheat menu, or you can go to Stefano's house (The intra-forest one, with the wolf in a cage in the house.) There's a stump out there near the entrance to his house. Climb up there somehow, (Stack a crate or rock or something.) and walk around on top of the stump. You're teleported to a very, very small island somewhere off the coast, with a teleporter back, a magic axe, and a chest of about 200 Guilders, which happens to be locked. (Maybe Stefano's house has the key? *shrugs* .. But best of all, ... walk along the northeast coast of that tiny, tiny island. It's kinda hard to find, but you'll find yourself walking on a TIIIINY path on the water. Follow that up as far as it goes, and you'll find yourself reaching a hidden cave. Go through there, and you'll find yourself in ... well.. I'm sure you all know. ;-D It's a pretty darn awesome secret. I'm not sure where the key to the armory is though. Tiny chance it's the one on Stefano's Mantle in his home in Moonshade, but who knows. -_-;