Black Diamond ATC

Pros: Lightweight, easy to use, and versatile belay device.
Cons: Can be hard on the skin, and awkward in wet-cold conditions.

While I, of course, am a perfect and flawless climber, sometimes the mere mortals I climb with fall off. This means that I have to hold their fall. I've found that a belay device comes in quite handy. OK, I'll be serious now. The Black Diamond ATC (Air ...

Pros: Light, Simple to use, Standard in belay devices
Cons: none

The Black Diamond Air Traffic Control device is the standard in belay devices. It is well made, extremely easy to use, and can be found on climbers everywhere from the popular indoor rock gyms to the gnarliest 5.12 big wall routes. Every beginner ...

Pros: Friction variable ATC. Makes belaying a breeze. You'll love it!!
Cons: None

I used to be a rock climbing instructor, and a facilitator at a local climbing gym. As such, I was always belaying persons while teaching. I used to use the old ATC and it was always tiring after so many belays. I would end the day with a sore arm ...

Pros: Easy to use; the new ATC-XP offers even more versatility
Cons: The ATC-XP is slightly bulkier than the original ATC

After using the ATC for many years (and recommending it to others), I've now picked up the new ATC-XP, and like it even better. The XP version can be set up 2 ways: turned one way, the brake runs over a smooth surface of the device that's identical to the original ATC. Turned around 180 degrees, the brake runs over a notched surface, offering more friction.
I've found that the higher friction side offered a smoother, easier "catch" when belaying a leader-fall. The stress on the brake hand was reduced, yet the stop wasn't jerky for either the belayer or the leader. The high friction option is also great when rappeling on a thin rope. However, it is overkill when rapping on a 10.5 -- unless you think you're going to need to stop to pull some pro or something on the way down.