I have the Performance basic one on my road bike, but the Crank Brothers big one on my mountain bike. I also have the Park Tool minimalist tool, but I have not carried it in a long time.

One thing though; I have been riding for a long time, and I have never ever broke a chain. And this is why I don't carry a multi-tool with a chainbreaker on my road bike. And I have been using chains with KMC missing links for a long time.

Is chain breaking really a "present" issue for roadies? I mean, I can see with mountain bikers, due to the uneveness of terrain, but roadies?