I know this reply might be useless since the post is so old, but I would think an elbow crack would be the most impressive. A nice slow lock and pop. Looks cool too.

Hi all. What's crackling? As a lifelong joint clicker and knuckle cracker I'm excited to discover this community.

When I was little I was told not to crack my knuckles but how can something that feels so good be bad? I've always felt pity for those who don't, can't, or won't pop their joints, like they're missing out.

To business: I can pop my right thumb and left big toe pretty much whenever I like for as many times as I like. What's up with that?

Crackle on.