Bit of insulating tape, permanent marker, and _adhesive_ heat-shrink tubing. The adhesive (basically hot-melt glue) in the heatshrink stops the heatshrink coming off (much like Ari's plastidip, I suspect). I bought this last time, but it wasn't quite so expensive then...
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You may have problems using it as a pull-through rope.
You probably will have problems trying to abseil off the end of it (for canyoning etc) through a device like a Stop (while probably not providing any real protection against abseiling off the end accidentally).