Bro

Either:
1) An awesome person who you have total respect for. It is used with lacrosse players a lot. They must have earned the right to be called a bro.

2) If used in a negative way it could mean a total douche bag. He is the annoying loud guy at a party. It is usually used in a sarcastic way like saying the person is cool.

1) Bob: He just did a back flip!

Joe: What a bro.

or

Bob: Hey man.

Joe: What up bro.

2) Fred: HEY EVERYONE IM AWESOME!

Charles: Wow, you are such a bro