People on online multiplayer games and such who see someone using an item or some other such they really want, who then pester the fuck out of that person in a desperate attempt to get it.
God, I dealt with this alot back when I was heavy into Diablo 2. Before I quit......for like the 20th time, I had a super high level Barb, and some kick ass equipment to go with it. In the game, it's common for people to start up trades just to check out each others equipment for various reasons. Well, one day, I was playing with a few random people. Well, one person asks me what equipment I'm using after a dungeon run. I intiated a trade to show him, and the guy freaked the fuck out about the weapon I had at the time. He REALLLLLLLLLLLLYYYYYYYY wanted it, for whatever reason. He offered me a bunch of stuff that was quite a bit less than the value of the weapon I had. Not to mention, I had nothing to replace it with if I did trade it.
Any who, I left soon after he started full on begging me to trade. Joined another game soon after and guess who appeared in the game a few minutes after I joined?......Ugh....... He ended up following me to 3 other games, begging for me to trade the weapon when I finally just logged off. Thankfully, didn't see him again after that.
Most recently, I have had to deal with people pestering me about wanting me to trade my legit Shiny EV trained Charizard in Pokemon Black 2. I don't go around bragging that I have it, but anytime I make mention of it on a Pokemon based forum, like on GFAQs, it doesn't take long for me to get at least a couple people PMing me wanting it. Thankfully, noone yet has been as annoyingly desperate about it like the D2 guy, but I have had people asking for the Charizard for free, which annoys me almost as much.