Here is one of my favorite tools that used to come in very handy at work. We always called them "transfer point pliers" unofficially at work, but they might have an actual name that I'm not aware of. When laying out sheet metal, I sometimes found that scribing or center punching the workpiece wasn't possible (or wasn't desired as it would alter the finished project by leaving dents or scratches). You simply take a pair of Linesman pliers, weld some rod to the jaws that is drilled and tapped for a machine screw, then add a pair of machine screws (one on the top jaw, one on the bottom jaw) that have been sharpened to a point on the end. This pair uses 1/2" diameter rod and 1/4"x20 (TPI) stainless screws. If you're laying out a complex pattern on sheet material, you don't have to keep flipping the workpiece over to make sure there are marks on the other side, and you don't have to worry about leaving permanent marks on the side that will be seen. The capacity of the pliers I made is between a 6" and 7" throat.
Sorry I forgot to take a few pics before it was welded. I was concerned more with shooting the video, which is listed here:
http://www.youtube.com/watch?v=AHUI1pola9A