Otterbox Commuter with Seidio Active holster...on my belt...with OEM wired blackberry headset from the curve. Headset keeps the phone nice and clean in the holster and my hands free to do work while I talk or listen to music. The cord on the curve headset is long enough to go from my belt around the back of my neck, so it stays close doesn't get caught on random stuff. I've been using this headset setup for years. For the 9900, OB Commuter and Seidio Active holster is a great combo.
Currently still sticking with the clip pouch that comes with it. I've been carrying my phone on my hip for 12 years and it's a habit I cannot break. In fact, I didn't get a BlackBerry about 6 years ago due to the size of what I would have on my belt. Now that I'm on my 3rd BlackBerry, I regret that decision. This new Bold is just the best for my needs/wants that I've ever owned.
Cheers.
I carried mine naked for a couple months but I just got the white and grey POP case from casemate! I love it. Reception has been fine and my berry still looks sleek and sexy, now its just protected!