I took a stop into Half Price Books today after lunch and scoured around. Lo and behold, they actually had software in the clearance section! I didn't know what to expect - and there it was! The 7th Guest for Mac! I had always heard about this game but never played it. And it only requires a 68k Mac with System 7!

It didn't come with a box, just the jewel case with manual and both CD-ROM discs in immaculate condition.

Of course, there's a Wiki entry here.

(Non Mac related conquest: Unreal Tournament for PC for $1, and a nice handful of records.)