^ So does that mean it's probably shot and I need to get a new crank? I've never greased it, but it came from another bike and I have no idea what someone else might have done. And I've read about putting a little locktite on them, but this is a mountain bike that sees trail use and the occasional 3-4' drop, so I don't want to chance a quick fix and a crank breaking at a bad moment. If the crank is shot, is it just a matter of fitting the spindle snuggly and the locktite trick would be safe to try, or is the arm weaker and I should just turn the left crank into a bottle opener?

Mbbiker, thanks for the advice. I don't think it's the BB, though. It's a new sealed Shimano BB in a new frame installed to proper torque and it Really sounds like it's the left crank. And I've listened closely due to having read several squeak/creak threads in the past.