For me, there are three.
1) Advantage leading to a goal. That's the very obvious one. In a game where goals are normally not plentiful, being able to let play continue to allow a goal to happen is a good feeling.
2) Cautioning for persistent infringement. This has always been a weak area for me, so when I do recognize it I feel like I'm improving. Plus, I think this is a situation where if you can recognize and deal with it, the players will feel like you are protecting them and won't feel the need to retaliate on their own (admittedly, this doesn't always happen).
EDIT - 3) As an AR, being able to recognize a ball completely over the line for a goal. I had one of these last fall where I was able to flag for a goal when the ball was above the keeper's head in a U12 game. I always like this call because it rewards me working hard to get to the goal line and being able to sell the call from the corner flag.