When I built up my six pack, I had it in the work stand, headset and forks were fitted (Fox Van 36). putting the cables and hoses on, I turned the bars to check the length and found that the rebound adjuster in the fully out position was just enough to cut into the paint under the down tube. The worst part is, with the rebound set where I like it, it just clears. If only I'd set the forks up first!
Still, second ride out I got a huge rock bite on the downtube just in front of the bottom bracket and it's been like that for the last 4 years!
I know of a chap who take a screw driver to a brand new bike and intentionally puts the first scratch in so he doesn't have to worry and can just get on with riding!