My most satisfying moment in GTAO is very simple really.
Couple of friends and I were driving around town in our new cars. Enjoying the sounds and the sun, when I noticed three dots moving slowly towards us. We weren't driving that fast so I just assumed this was another group of friends cruising around.
I was right, but they were in tanks. Found that out the hard way.
My friends quickly spawned and ran down into the subway station. I entered passive mode and taunted the tanks a little. Quick jerk off, air thrust, you know the deal.
These three tanks were not impressed with us. They were looking to spawn kill, so they waited around us. Shooting at me (with no impact) trying to shoot into the subway. It was actually quite funny.
One of the tank drivers got out of his tank and walked up to me doing the "up yours" motion then heads underground to get my friends.
I ran over to his unattended tank. He quickly realised what he had done after going down about a flight of stairs. He ran back up only to get shot in the face by his own tank piloted by me. I called lester, went off radar and destroyed both of his friends from behind. My friends came back up, called their tanks and we spawn killed them till they left all while condescending them with rude and unfriendly comments over the mics.
They were so pissed off.
It was the most satisfying moment ever.
Call me an asshole, but those dicks deserved it. I know I was just as bad as them in the end but I got some of the best laughs out of that so it was worth it all day. I never use tanks so it was a fun change, and besides, it's GTA.