Well, since - as GM - it's my job to make the players have fun, it must be their job to jump on the train, go where I send them, react according to my script and bloody-well have fun.
Now, seriously:
My biggie is that the players do not behave like the game is
The [insert player name] Show with all the other players and any NPCs they encounter being, at the very best, supporting actors - if not merely bit-players.
I've played with people, and had others in my games, that charge around the game universe with the attitude that they can do whatever they like and everyone else - fellow team members and NPCs alike - must just accept it... after all, (s)he's the
STAR(it really needs a border of animated lights) and therefore every all the "goodies" are automatically on their side, regardless, and NPCs still have to give you the helpful information, assistance and absolute loyalty no matter how much of a prat you are...
Everyone's there to have fun, not to play second fiddle to a grandstander who wants to live out their fantasy of being the biggest meanest badass on the planet without any fear of the consequences that that sort of behaviour would attract in the real world.
I don't mind character's surprising the hell out of me with strange and unusual approaches or even doing the Big Damn Heroes shtick or doing things because it'd "be/look cool"- leaping over lava onto a flying wyvern to help the party is all well and good.
I just expect them to be "team players".
There are degrees, of course. One player delighted in playing obnoxious, unlikeable characters - but his actions were never enough to jeopardise the security and safety of the team. They all cheered when his characters got killed (and the player cheered loudest of all), but they never were moved to want to kill him themselves. The characters were "quirky" in the extreme but at least had the redeeming qualities of being useful and not being so obnoxious that they became a liability.
Compared with other players whose actions made so many powerful enemies and alienated so many potential allies that the game rapidly became unplayable - or risked getting their own characters and the rest of the team killed - much to the annoyance of the other players and the GM.
A number of them were killed by their own teams - much to the surprise and dismay of the players in question as that didn't fit their "it's all about me" attitude. After all, they're the badass anti-hero STAR of the show...
I hate having to think up ways of avoiding a TPK that would not have even been likely to occur if it weren't for one grandstander going to extraordinary lengths to honk-off everyone within 200km...
