People who are challenging

When was the last time someone challenged you? Challenged what you believe or challenged you to live out what you say you believe. I think, if we are not careful, we have the tendency to surround ourselves with people who think just like us. We want to hear we are right. The equivalent of being surrounding by "yes men". We respond to something and we want people that will agree with us and justify our actions. Strength in numbers and all of that. What I am finding out though is that the people with the most differences from me (whether it is personality, beliefs or thoughts on how to accomplish something) are the ones who help me learn the most. Not saying that I always like it, but it is a good way to refine what I believe. To be able to explain my thoughts to someone who is drastically different from me or has a whole different set of beliefs requires me to really know what I believe and to be able to communicate that. I have some people in my life who challenge me at my request, others who challenge me by who they are, and a few who do both. Who challenges you? Do you appreciate it or would you rather not deal with it? Feel free to disagree with me.