I've heard great things about the Rawlings line of nylon wasters, but haven't handled them myself.
I've used the "With Intent" nylon wasters, which I really, really didn't like at all (though they're gone now, from what I've heard). They were tougher than a wooden waster, but they didn't feel anything like a real sword. I can get over that (wooden wasters usually don't feel realistic, either), but they were way more expensive than a wooden waster (around $120-150). That's getting close to the price range of the lower end steel blunts. I hope the Rawling line is a better value for the price.