What are you guys using for antenna wire? Also what are you using to tie them down with?

Anyone?

I use copper wire for antennas.

I often use guitar strings because they tend to stay nice and straight, plus I can leave a bit of the windings on one end to simulate the spring many whip antennas are mounted on. It's cheaper than AM antennas and better-looking (IMHO) than the old stretched-sprue thing. I haven't had to do any antenna tie-downs on any of my vehicles, but maybe fuse wire might be fine enough.

Brass wire and styrene rod would be excellent choices.

They retain springy properties so that they if accidentally bumped will spring back.

Also, as seen in some WW2 armor but mainly modern armor, they
can be tied in a curve and look very realistic.

Problem with copper, it is too soft and once bent, won't
spring back.

Cheers,
Joe

What happened to just stretching plastic sprues ?

They break, and are hard to get consistent results with to-scale thickness.

There's nothing wrong with using sprue, I just tend to prefer my son's used guitar strings for the reasons I mentioned above.