My century bikes have all been fixed trackbikes.
The first (2) centuries I did (The Prouty)were on an old ('99) GT 'Pulse', which I sold a few years back- I was the second or third owner of that bike.
I did The Prouty last year on a Cannondale 'Capo', running 48x18- my knees were angry at me for almost 10 months after that.
This year's Prouty I did on a new IF Pista (
http://www.ifrider.com/?s=pista), and last weekend I did the Seacoast Century on the IF as well.
The Workman cruiser (1-piece cranks? wow!) gets my award for most kick-arse century machine!