One of the more annoying jumpseat experiences I've had involved someone attempting to bump me from the jumpseat of my own airline.
I had reserved the jumpseat through our system, and was already on board when the gate agent came down and said, "There is a jumpseater at the gate who is more senior to you." I informed her that #1, I had reserved the jumpseat, and #2, seniority (at my airline) has nothing to do with the jumpseat. If you don't reserve it, it is first come, first served within your priority class.
Anyway, she said, "Well, he wants you to come up and talk with him." Because I'm not a jerk (most of the time) I agreed to walk up and speak to him. He was a mainline guy in uniform. I said, "Hi, how are you doing?" and he said he was trying to jumpseat home. I told him I was too, but I had reserved the jumpseat. He said, "You work for XXX?" and I told him yes, and he said, "Oh, well I guess I'll move along." I told him to take care, and went back to the plane.
It is a good thing the guy left the gate because when I got back down to explain what had happened, the captain was irate. At least the guy recognized that he couldn't bump us on our own metal. It was just annoying for him to attempt to play a game that he knew wasn't cool. OAL never is by seniority, always first come, first served. Even company pilots can't bump someone due to their seniority here. Oh well.