time to rant time to rant....god I love doing this...I know some of these have already been said, some more than once, but some of these just can't be stated enough no matter what they are:
Players who try to tell the DM how to run his game.
Players who complain when the DM hurts their character in combat.
Players who complain when they are told that the game is not a hack-fest but they make combat machines anyway and then complain because there isn't enough combat to satisfy them, and then when there is combat they complain that they feel they are being railroaded into it.
Players who play the same character over and over and over again, no matter what race or class it is.
Players who don't try to roleplay at all.
Players who sleep during the game, play video games (this one really pisses me off), or just stop paying attention. I put a lot of hard work into the game, and I'll be damned if a player is going to start playing a video game in the middle of a game.
Players who complain that writing or typing a single page background is too much work. If I can plan for six to eight hours a week on a game, then coming up with a one page background shouldn't be too much trouble to ask.
Players who always go, "I swing my sword, did I hit. Cool, 10 damage." over and over and over again without trying to put any excitement into the combat. Talk about boring, bring on the cinematic action Puh Lease!
Players who roleplay loners, or characters who always leave the middle of combat just because they feel like it, and do this all the time...and then players who do this who complain when the other party members kill his character for ditching them so many times. When that happens I think its as funny as hell to hear the player wine and complain.
Players who make character that don't fit the mold or desires of the campaign structure...especially when they do this on purpose just to spite the DM.
Players who show up late, or dont' call at all to say that they will be late, or a no show. Very disresectful towards the DM who spent all that time putting a game together.
Players who don't move their own miniatures during combat.
Players who expect me as DM to know all the spells for them so they don't have to keep track of it themselves.
Players who leave in the middle of combat to have a smoke break.
Players who suddenly leave early and didn't tell me as DM before the game began.
Players who don't read any emails I sent to them about the upcoming game.
Players who are not prepared and don't try to be prepared.
ummmmm...I'm trying to remember if there are others, but for now that will do.
I really think that if any players only are reading this, they should really take this stuff to heart.