@Reverserbucket: No dogs have yet been implicated in terrorist plots, therefore dogs are not checked.
On the other hand, the general rule is that if it is not allowed, it is forbidden. And don't expect consistency.
On a recent flight I had an adjustable spanner ("wrench" for some of you) confiscated. This thing was all of three inches long and about as offensive as a ballpoint pen. However, a new ruling said that "tools" were no longer allowed in the cabin.