Editorial – Every gamer knows or has been that guy at some point in their life as a gamer (and probably real life, but that's a topic far to vast to discuss today). Sometimes players are oblivious to the fact that they are "that guy" while other times the revel in it. Vagaries aside I'm going to break "that guy" down into some of the more offensive behaviors. I'm going to refer to these archetype as guy because it tends to be the dominate species in most environments however female gamers are just as likely to fall into this category.
You know the guy, he sits down at the table and wants to dominate. To him a game is about more than winning, he must absolutely crush his opponent and ring any enjoyment they may have out of the game. Typically this is the guy that looks for the most broken degenerate combo and then preys on new players. How many games have died at your store because of this guy? In multiplayer games this type of player will typically pick one opponent to be the victim of their wrath and pound on them until someone else does something to slight them. Many times these perceived slights carry over through multiple games and eventually lead to the victim either leaving the play group or just giving up every game. Of course many times this will lead to multiple players mutating into The Destroyer which is just bad for everyone.
The Man with a Plan
"Dude, if I only had 2 more turns I was going to ______________." How many times have you heard this come out of a players mouth? How long after they've been eliminated from the game do they continue to blabber on about there "secret tech" that would have one them the game if only X would have happened. This guy is probably one of the less offensive archetype, however they tend to push everyone's limit of tolerance. This is the guy that will corner "an experienced player" or anyone who it to polite to walk away and babble on about some "sick combo" they figured out (many times upon further investigation, whatever awesome thing they're rambling about doesn't actually work that way).
Every had a game that typically takes 45 min or less drag on for hours? It's probably because you have this guy at your table. Sometimes I like to give them the benefit of the doubt, maybe they're really thinking about there next move (if they win lots of games that's probably the case) but many times it's because they didn't think about what they're going to do while waiting for their turn. Sometimes they just move slow, aren't paying attention or are consistently distract by "the man with a plan." Whatever the case they drag games on excessively which in turn limits the rest of the table. In competitive settings this player can cause you to lose games just because you never got beyond turn 3 in any game.
The World Slayer
This guy tends to come up more often in card games like Magic, however some tabletop games give them the option to wreck everything as well. For some reason this guy just likes blowing up the current board state. Typically this resets the game and drags it on, especially since many times this player doesn't have a plan for what they want to do after they blow up the world. The resulting game degenerates into a race to beat down this player due to shear lack of forethought on their part. Other times this player will simply kill the entire table with some ridiculous combo, which is fine if they win the game not so much if everyone loses.
You know this guy, if the game isn't going their way everyone knows about it. Cries of "that's so broken, why are you attacking me, blah blah" vomit from their mouth throughout the games regardless of what's really going on. When they're not whining about something they threaten other players with repercussions to every action, or broadcast their opinion of what they think another player is trying to accomplish to the world (regardless of if they are playing or just watching a game). This player tends be be spiteful and will with their last action in a game do whatever they can to ruin the rest of the table's fun. This includes but is not limited to making a play that drags a game on, blowing up the world, packing up their terrain, and any other act that is comparable to a three year old's temper tantrum.
Hygiene matters. I don't care if you shovel shit for a living and love the smell. The rest of the world is far from enamored with your stench. Daily showers, deodorant, regular laundering of your clothes, properly wiping your ass are all things to make the air we all have to breath more pleasant. This typically only comes up at game stores or public venues (because most people will spray air freshener or something to indicate there is a foul odour). It dosn't matter if you're the nicest person in the world, if your presence is heralded with a rotten egg and curdled milk stench nobody is going to want you around. while people may not say anything to you directly, you can be damn sure it's the first thing they talk about when you leave.
Looking at these archetypes I'm sure you can find at least one person in your group who falls into one of these categories. Sometimes one individual falls into several or all of the above which is unfortunate as they are most likely making games suck. If you yourself are falling into any of these categories, do yourself and your group a favor and stop the offending behavior or at least curb it. Most of these behaviors are pretty conscious behaviors that should be relatively easy to manage.