I've got a 12" and a 24" dial caliper. Off brands, well not Starrett or Mitutoyo anyway. Mostly I use them for roughing in larger mold blanks to length. Once in a while I wish I had something longer. I can use the mill as a measuring tool, and I can use gage blocks and 123/246 blocks to block up the end of a part, but what I really want is a half decent (or doesn't totally suck) 36 inch caliper. Its much faster than cranking the mill table back and forth or setting up blocking to measure with a smaller tool.
Well, I guess I'll want in one hand and save pennies in the other...