Cannondale makes a bike they call the Bad Boy. It’s an “urban” bike in the modern parlance, built along mountain bike lines, but with slicks for fast city riding. I’ve wanted one.
At the same time, I had my old, custom, rigid, mountain bike hanging in the garage. It was pricey and high-tech in its day, with a Cannondale 3.0 frame, a Ritchey Pro-Logic fork, Mavic cranks and an otherwise Shimano XT drivetrain, and a whole lot of other Pro-Logic parts. It weighed under 24 pounds as a mountain bike, which was pretty good. Maybe the amazing thing is that we used to ride rigids like that everywhere. I even took that thing down Mammoth mountain in the old days, along the Kamikaze route.
Anyway, I dug out and washed off that bike yesterday. It was in better shape than I remembered, with truer wheels than I feared. It was all good enough that I went off to buy some Ritchey Tom Slick city tires (26×1.4) and set myself up an urban bike:

I just went for a 20 mile spin and had a lot of fun. It’s actually the lightest (20-22 pounds) bike I’ve got right now, and with the slicks the easiest rolling.
I think I’ve got my in-town beater. It’s a little twitchy on the steering with the slicks, but I’ll pay attention. The narrow handlebars are kind of funny too. They were all the style back in the day.
Update: I forgot the weirdest element of 1980’s light mountain bike technology, Ringle’ skewers and seatpost quick-release. They are light, but the funny thing is that they don’t really work in the “cam action.” You’ve got to use two hands and snug them down by the threads, screwing them tighter. The photo also shows the well-used aluminium/carbon-fiber seat post:
