I bought a metal wire that just looked like a tank tow wire at Hobby Lobby, but it is way too stiff. So I’m looking for an alternative. What do you guys use?
Picture hanging wire. Its cheap and very bendy. 
I use Eureka brand cables, they come with the resin ends/eyes specific to many different vehicles. I get from evil-bay and they are not prohibitively costly running for between $5 and $8.
I make my own from very fine wire sourced from computer and telephone lines. I’ll insert 2 to 3 (for 1/72) in a micro hand drill and secure the other end in a micro vice. Turn the drill and the wire is braided evenly.
I recently purchased more than $100 worth of metal barrels. So I cannot justify spending more on tow cables although Eureka cables look awesome. Cheap hanging wires look more realistic than plastic cables. For thinner cables, I’ll try making my own using telephone cables and a Dremel.
Parachute cord… inside the nylon sheath are braided lines that work perfect for tow cables in 1/35. The cord is pretty inexpensive (since I no longer have access to the free spools from our Riggers) and one 50 ft batch will give you enough guts to equip a lifetimes worth of builds. I cut it to the proper length, super glue on the ends and boom, another tow cable.
Another good substitute is solder wick. Just roll it between your fingers for the desired thickness. It is very workable and has a good “cable” texture when finished.
Guitar strings. My local music store does re-strings and is more than happy to give me the old ones.
Guitar strings are not bendy enough for me. I use them for antennas, though. D’addario 0.011 strings are perfect for 1/35 scale AFVs.
Solder wire comes in a variety of guages and can be twisted to look like cable. Solder is soft enough to make in-scale realistic bends in them.
I just bought a picture hanging wire. I guess it needs to be a little bit twisted to look more realistic.
I do have lots of solder wires and will experiment with them.
Kite string works well, and no “hairs” like other nylon string.
I’ve also stripped the insulation off automotive wire and used it after a slight twist. I strip it by melting the insulation, which also anneals the copper wire. If you use wire from low-voltage circuits, it’s finer strand and looks good.
I used wire from audio speakers in the past. Works really well, seem realistic and can easily be bent.
Best parts is the really low price for a lot of it.
Here’s a how-to tread I did in the scratch-building forum years ago with a few pictures of one:
http://cs.finescale.com/fsm/modeling_subjects/f/44/t/77955.aspx
Hope it helps!
28 gauge fake flower stems. don’t have the twisy looking effect but primed, painted Tamiya metallic gray and dirtied and rusted up and they look ok. easy to bend for those weird arrangements like IDF centurions.
I’ve used jeweler’s wire in the past, usually craft stores have a variety of different types, but they should have one that looks braided. More recently though, I picked up a set of tow cables from E.T. Model, which seem to be working well.