What is the common ground shared amongst atheists, agnostics, theists, etc.?

In reference to this response from this question, what are the points of agreement you share with someone of a different or opposing belief system?

For example:

As a theist, the common ground I share with an atheist is the need to verify information before believing it is true.

As a theist, the common ground I share with an agnostic is the feeling of dealing with the elements of uncertainty.