1983(?) Cannondale ST500. It's my go-fast touring bike.
Notable because it was one of the first mass produced aluminum bikes--a rarity in those days. Hard to believe that aluminum frames were hot stuff back then. Sold for $595 retail! Sure I like lugged steel--I have a Raleigh Kodiak I'll post later--but something about the simplicity and stealthiness of the Cannondale really appeals to me.
Hey, it even made it into Rydjor's Bike Collection:
http://collection.rydjor.com/bikecollection/1983can.htm