Many years ago I saw Penn & Teller and Penn Jillette talked about how juggling flaming sticks or knives isn't that impressive because they are perfectly balanced for juggling.

Instead, he took three large whiskey bottles of different shapes and sizes. On stage, he broke the bottom of each bottle. They came out all sharp, jagged, and uneven. He then proceeded to juggle three of them. I think he got only a few rounds before he was forced to drop them.

I don't think he does that anymore.