Here's another one. Say you're really upset with him, for whatever reason. There's the impulse to either stay quiet, for fear of getting ridiculed or laughed at, and there's also the impulse to rush right up to him and tear right into him. Instead, you remember that, as your best friend, he by definition has your best interests at heart. So, you go up to him, inform him that there's something that's really bothering you, and carry on a rational discussion about it with him. Why? Because you trust him to help you deal with this. If he loves you, he will do whatever he can within the bounds of honor for the two of you to get past this. If he was in the wrong, he'll apologize and work not to do that again. If you made an incorrect assumption, then you will apologize to him and remember not to make such assumptions again. Either way, as long as the two of you continue to follow the Golden Rule and the Scout Law, the end result is the same.
There are many other examples, of course. The bottom line is that you two trust each other implicitly and totally...with anything.