We have an office bicycle.
It was a stray 1980's GT mt. bike that spent at least 1 year in the woods before I towed it 4 miles into the office on flat tires.
One night, during a software roll-out, my wife came by the office and whipped up some "DEATHMOBILE 4.(skull)" graphics and a skull for the head tube while I taped up and took apart the bike for refinishing.
I got 2 cans of $1 spray paint and painted the wheels/frame up rat rod style. The tires were pretty much rotted off, but I found a $5 pair of NEW whitewalls on the back wall of a sporting goods store a few months after the initial build. Grips were rotting off, so I wrapped the bars with some of my white hockey tape. Everything that was broken on the bike I simply removed (sometimes with a hack saw.) There are about 6 functional gears in the back. Couple of skull valve caps and a couple of skull license plate bolts add a little subtle style. So we're talkin' about a $10 bike here.
I'm watching for a free/$1 shorty chrome rear fender for it. I know, Chrome don't get ya home, but I think it would add a little more style to the bike.