I often carry a scuba regulator. For those unfamiliar, it's a 3-4 foot hose with a 2-3 lb chunk of metal at the end. I'd choose it over a knife or billy club any day. But TSA says they are fine:

"You may bring regulators, buoyancy compensators and masks, snorkels and fins as carry-on or checked baggage."

When asked if I have anything that could be used as a weapon I hedge my bets and simply list a few items I have without saying "yes" or "no"

TSA: "Do you have anything that could be used as a weapon"

Me: "I have pens, pencils, a few books, a scuba regulator, keys."

I've never had them even give a second look.