Powergamer
"Powergamer" is a term describing players who are interested in winning and, more to the point, winning big. Exactly how they do this depends on the game.
Powergamers who play RPGs generally attempt to make their characters as effective as possible within the game mechanics, possibly (but not necessarily) by exploiting broken or badly worded rules. The term is usually used pejoratively, suggesting that the player in question only cares about the mechanical power of their character and this comes at the expense of roleplaying, although there is nothing intrinsic to powergaming that inhibits good roleplaying.
In Magic: The Gathering, powergamers are also called Spike or "Spikes", a name chosen specifically because it sounds all Serious Business and boring. Ironically, "power gamer" is the title of a much different type of gamer.
In wargaming: powergamers are less likely to be referred to as such due to it's association with level-scaling systems, and are typically referred to as "tourneyfags" which is a far more negative term. Though the term holds virtually the same meaning, as tourneyfags tend to focus entirely on a rule's usefulness on a tabletop and are (usually) disdainful of gimmicks or underpowered units.
A somewhat milder term with a similar meaning is "optimiser", which generally lacks the negative connotations of powergamer, in that they won't typically suck the fun out of anything they touch.
Munchkins
At the other end of the scale is the "twink" or "munchkin", which is almost always used to refer to someone who cares only about mechanical power (to the exclusion of roleplaying), or is willing to outright cheat if he thinks he won't get caught, or there will be no consequences if caught, as is demonstrated by the "Munchkin" series of card games by Steve Jackson Games.
Everyday powergamers are easily forgiveable, since there is a healthy respect for the way that any given game system functions, and their actions are perfectly excusable since the rules allow (and can be argued "encourage") them to do so. Depending on the setting or ruleset, a powergamer can garner a healthy measure of accolade for coming up with new levels of "optimal" play.
By contrast, Munchkins have a marked tendency to be more creative in their interpretations of rules; where a typical powergamer would look at a ruleset and use it to their maximum advantage, a munchkin's typical response to their detractors is that nothing in the rules say that they cannot do something.
In wargaming, the equivalent to munchkin would be WAAC (Win At All Cost) players, who focus almost entirely on overpowered/broken units or rules, rather than attempting to create an efficient or optimal army list.
True Munchkins rarely, if ever, gain positive recognition for their accomplishments.
Identifying a Powergamer
Everyone who plays a game with a rule-based system (whether competitive or cooperative) is a powergamer to one degree or another. As everyone who plays wants to do their best and so long as people know the rules they can understand what is comparatively better than another, so unless someone gets a kick about playing the underdog or seeing others outperform themselves, it's simply in the nature of the system.
Habitual powergamers might argue that they are not powergaming at all and that they are just playing the same way as everyone else, but are easy to spot based on their behaviour, which is generally the same regardless of which system/ruleset they are using.
In systems which undergo regular revisions or receive frequent updates, powergamers will often stand out due to their fickle attitudes. Often becoming obsessed with the next "new" rulebook/codex/splatbook which will either be an improvement over anything previously released or is new enough that it has not been effectively countered or debunked by the community at large. In these situations, a gamer who requests a re-roll of his character or sells his old army on ebay to fund his next one are generally going to be powergamers.
- Note: it doesn't have to be freshly released rules or player options to count as "new", but can also be from the point at which the player discovers that he can do something new that he starts changing his attitudes in favour of his latest obsession.
Lack of imagination when it comes to character/army builds is also a clear indication; people who hunt internet forums/help-sites for optimal builds tend to be powergamers, as it shows that the player is more interested in "winning" than actually playing the game in their own fashion. (see the rage summary below) Powergamers who also rely too heavily on public-domain builds can also reveal themselves to be poor players and tend to have the most difficulty adjusting when someone else presents them with a unique situation or when new rulebooks get released (but then they jump ship)
They also tend to be quite vocal in their disappointment if they or others alongside them are not playing "optimally". For example: in RPG sessions if the group healer is not playing a build that they think is optimal for healing and could be bringing the group down. This is extremely visible in MMORPGs where non-optimal players tend to get kicked from raid groups. On the tabletop, they'll tend to complain that their losses during games are because they don't yet own the right combination of models/units (but will "soon") or that you cheated. (Either way, it's not their "fault" that they lost)
Considering the issue from a different angle, Powergamers usually like to brag about the efficiency of their characters, putting emphasis on the hard work necessary to create the apex of whatever class or concept they chose. Interestingly, as soon as it is touched upon the extreme efficiency-build, they usually get very defensive about it. Watch out for someone defending their character as "not imba" before the acquisition is made.
Taking this further, players who get called out on their powergaming will often go to obsessive lengths to tell you how their character is NOT the result of powergaming or munchkin-fu and will have a defence seemingly prepared before the question gets raised. They'll often immediately go into great detail about what their character is bad at, or cannot do as well as other party members to try and convince you why their character is balanced. Unfortunately for them, this has all the hallmarks of being a powergamer anyway, because obviously they've considered the issue at great length before getting into the argument; it's like they think fact that they have a Dump Stat deserves positive recognition and would be like pointing out their Wizard cannot fight in melee as well as a Warblade, when that wasn't really the issue in the first place.
In Summary
If you've played against one in any game, was it fun? Did you like having your balls ground to a pulp? Fuck no. Nothing is worse than that guy who spams Abaddon AND Kharn AND three fucking Land Raiders because of a technicality. They're all dedicated transports? FUCK THAT NOISE, GTFO MY STORE. Or they guy who manages to get 4 5 6 7 riptides in a single list because of GWs shitty wording that all have FNP.
Ever played against an IG armoured list. No? Pray you never do, because that list displays a level of asshattery (and disposable income) on a godlike level. Seriously, fucking TANKS as TROOP CHOICES?! OH FUCK THE FUCK OFF! Necrons don't care though so... Allies much?
Did you know that it's theoretically possible for a player in the original World of Darkness to have the powers of a vampire, a werewolf, and a mage at the same fucking time? Why even bring a fucking party?!
For anyone playing a game simply to have fun and enjoy a good story, a powergamer is your number one enemy. Avoid at all costs. They'll fuck your shit up six ways to Sunday and five ways to Monday simply because they can.
Dealing with Powergamers
In Roleplaying
A GM of a party with a munchkin/powergamer can be quite tricky, since it can radically unbalance the group in many situations. For example, if he's somehow got himself infinite (figuratively speaking) armor-class then introducing a hard hitting counter to him could be absolutely devastating to the rest of the group if they aren't also powergamers.
Best thing to do would be to speak to them away from the gaming table and discuss winding it back a notch, or at the very least concentrate his powergaming efforts onto just one thing in particular and stop being a do-it-all mary sue. Unless your powergamer is a dick you may find that this works best and keeps tears to a minimum.
Failing that, you can always read their character sheet to see precisely what will work against them, though this may require a lot of work on your part to piece it all together. The unkillable party tank may be weak against compulsions or fear effects, or the god-like wizard becomes useless in a magical dead-zone or wild-magic area, which would force him and the party to come up with more creative solutions rather than "throw the powergamer at it"
If that doesn't work or if you cannot find an easier solution, then a stern reminder is in order. A powergamer is beholden to the rules of the game, even if he twists them to his own advantage to create something more powerful than the sum of its parts. A GM is not, you are the Neo to the gamer's Agent Smith and you can invent things on a case-by-case basis to give the powergamer a spanking.
- Unkillable PC Barbarian? Meet the "actually" unkillable barbarian with axe of instant death, he kills you but the party's weak-ass rogue could one-shot him to death by stabbing him in the neck. That's not in the rules you say? I'm the GM and can rationalise whatever I like in the world I built. That's not fair you say? Did you really think I'd let you walk over my game every week? Is that you Oberoni?
Can be harsh, but if your GM style is not harsh in the the first place (i.e: anything other than Killer GM) then your players should have realised that powergaming was absolutely unnecessary in the first place and that there isn't really a "winner" in a game that only goes on as long as the GM can be bothered putting up with you guys.
In wargaming
Just don't play with them and make certain that other people are aware of the sort of opponent they are too, so your friends can make the same decision. If you get no enjoyment out of the game there is no point in playing, wargaming is not a job or sport that requires your absolute commitment. Your opponent will find that they have no-one to play with either. Whoop-di-do if they've got an unbeatable spam list if no-one will give them the smug satisfaction of beating people stupid enough to play against them. This goes double for true munchkin players who exploit bad RAW to get advantages they shouldn't have.
Failing that, if there is no-one else to play with in your area, or if you are at a tournament that kind of requires your participation. If you can't beat them... join them, unfortunately this means stooping to your opponent's level. If you need help there are plenty of tactica and netlists out there which can help you to build your army. Just don't let it go to your head.
Examples of Powergamers/Munchkins
- Comic Book Guy from the Simpsons, when he makes custom Pokemon, Digimon, and/or Yu-gi-oh trading cards
- Sheldon Cooper from Big Bang Theory, who also uses custom cards, but munchkins his way around a group ban on "home-made" cards by making them at work.