I dont know any gate agents, or related to any ... BUT
I probably get upgraded at no cost 1 out of every 3 Trans-Con flights just because I believe that I might be the most polite and pleasant traveler they will meet during their shift.
When I have the chance, I volunteer to bump, and even if there is room on the plane, they may upgrade me just for volunteering.
I am a pretty easy going traveler, and dont get upset at things they cannot control. Have learned that a positive attitude, no matter what the situation, is gonna be rewarded.
Gate agents can be your absolute best friends (which I prefer), or your worst enemy (if you treat them like $hit and have a bad attitude, then, thats what you get)