I just got it 2 weeks ago, so I don't have many good moments..
I guess there is two things that are.. somewhat cool.
I was a sniper, which I am really trying to get better at, headshotted an airborne scout who was trying to jump on top of the bridge.
Also, I was a medic, healing a heavy, he got 10 kills in about 14 seconds with a minigun. Yey for the medic + heavy combo.