I can’t truly say who originally asked this question, because it seems like I get it all the time.
What kind of equipment do you use?
So what’s in the bag, eh? To start, I shoot using Nikon equipment: a D700, a 24-70mm f/2.8, an 80-200mm f/2.8, and a 50 f/1.4, which I most frequently use for portrait close-ups (like headshots). I also have an 105mm macro that I sometimes whip out for close-ups of rings. The next lens I intend to get is an 85mm f/1.4, for similar-but-less wide imagery as the 50.
I once bought a Tokina wide zoom lens but found the focus was not as sharp or reliable as Nikkors, and there was more chromatic aberration when I used it, so I no longer shoot with third-party equipment. Third party (Tokina, Sigma, Tamron) is recommendable if you need the gear to get your business off the ground and some shoots under your belt, but not if you’re aiming for the highest image quality possible.
I also use a Nikon SB-900 flash unit, and occasionally an off-camera SB-600 flash on a light stand, triggered by PocketWizards.
Additionally, I consider Adobe Lightroom and Adobe Photoshop CS4 to be as vital tools as the camera and lenses. Every photo that you will ever see of mine has been in some way touched by an Adobe program. They help my work become better, faster, and easier. I heart my little digital darkroom. If you already own a camera and a lens and are trying to decide between an image editing program and another piece of hardware equipment, I’d personally recommend Photoshop over anything else!
TIP: Can’t afford Photoshop? GIMP is a similar image editing program (albeit fewer advanced features) that you can download for free. I can’t say I’ve ever used it, but I hear about it often enough.