I cut myself a piece of wood 1/2" wide and 1/8" thick and around 10" long (not that I need that much) and transferred measurements accurately onto it. It doesn't hurt when I press it into my skin like the other rulers did. It also sits inconspicuously on my desk and nobody questions what it is.
I bought a 12" plastic one with rounded edges and clear 1/16 increments and mms for $0.99 at a drug store. It's comfortable doing BPing. It does have a .31" gap before the measurements start, so I just add that to the measurement.
Mine practically has no space, but I have checked and it maybe cheats me of 1-2mm at most. I do have a metal one that has no space at all, but I'd stab myself if I tried to use that one as it is pretty damn sharp.