I think its good to revisit topics from time to time Tom. Here's my recent attempts, starting with what most would probably consider the industry standard.
1) Speaker wire from Radio Shack( the 3-pack of red, black and green). The stuff will hold a coil, but I feel it doesn't have the right "lay" to it aft of the pogo stick, more so that it is rigid and does not have a natural droop or drape to it.
2) The RS speaker wire again. This time, just the outer casing. This is great for the old-school, straight airlines but again, the stuff has a memory (from being on the spool) so it also lacks that "draped" look coming off the stick (maybe warming it and re-working it to the right shape, haven't tried that yet).
3) Telephone wire: this stuff is thinner in gauge and will hold a nice tight coil but looks a bit small in diameter.
4) Ear bud wire: Has a good diameter and seems to have a decent drape (in longer lengths) but is probably one of the more expensive options ($ versus usable length).
5) Paracord: This stuff is pretty cheap, looks the right diameter and comes in every color you could possibly think of plus three more. The only problem is it looks more like a fabric covered hose (I'd guestimate around 5/8" in 1:1 as I tried out as a 1" booster line on a fire truck reel and it came off looking too small).
Edit: I assumed we are talking the service hoses and glad hands
My conclusion, I tend to go with option #2, using the black wire casing (seems easiest to remove from the wire) and make three, old-school, straight lines, great for our older stuff but probably not what we're wanting for the more modern IH's and Petes.