So you want to kick butts and take names and you've got a character that has so many bonuses her fists count as weapons of mass destruction, but the other players in the group aren't happy with you. The GM keeps nerfing your character and instead of being impressed the other players just roll their eyes at you. How do you fix it?

Why should you?

The rules say you can do it, so why should you change? It's not your fault other people are bad at the game. Well, there are the obvious reasons, i.e. being a considerate human being, respecting your fellow players, and continued inconsiderate behavior resulting in no gaming. You may also discover that the game can become more fun when you let go of powergaming; things can become less adversarial, you spend less time crunching numbers, you have more freedom to relax and enjoy the game and the people you're playing with, etc.

Also, step back and think about why you want to use every loophole and show up everyone else at the table up. For some power gamers, there's some nasty emotions lurking there that are going to poison their gaming experience; fear, resentment, selfishness, inadequacy, anger at fellow players, etc. If you are power gaming at other players or in response to some negative feelings, that's a big problem and it needs to be addressed outside of play.

A Clean Start

A lot of being a good gamer happens in character creation. For power gamers, it's usually very easy to get moments to shine and get a chance to influence the game in character, so your challenge is to make sure that you aren't shutting down other players or stealing their moments. Limiting your options in character creation removes a lot of the temptation and capability to ruin other people's fun. Look at what the rest of the group is making and don't make a character of the same type as someone else to avoid overshadowing them. In areas where you do overlap with other characters, tone down your character so that it is not mechanically superior to the rest of the table. This does not mean that your character needs to be incompetent, just that it's going to be hard to share the spotlight when your character is better than other characters in the areas where they're supposed to be awesome.

Permission to not be a Jerk

You've spotted an amazing loophole! (or more commonly you read about it on the internet) If you combine powers from three different books with a poorly worded racial trait and a single level from four different classes you can get immunity to every type of damage in the system! And now that you've spotted it you know it would be stupid not to use the loop hole, even if it's not what you were planning on playing and the powers make no sense to combine together since they're from three different settings. It's rules legal! The internet said so. And if you don't do it, then someone else at the table will and you're going to end up playing second fiddle to mister invincible the whole campaign.

When this happens, calm down and take a step back and talk with the GM. Ask that they veto that combo. Then it's not legal at your table and you won't feel obligated to use it. In fact, if you're a power gamer talk through lots of stuff with the GM. Communicate with your GM what exactly your character will be capable of. If you have a question about whether something is rules legal or acceptable at the table, the middle of play is not the time to find out, especially if this is going to lead to a game derailing debate. Be willing to take feedback and make adjustments to your character to make the game work.

Odd Specialization

It's common to optimize characters for combat or stealth to render challenges trivial. Consider optimizing a character for something else that's less likely to interfere with the game. In fact, if you can find an optimization that will allow the group to move quickly through parts of the game that tend to drag, you can help the flow of the game. If your character is optimized to heal very effectively, you can keep the group in action and moving forward. If your character is really good at exploration, you can keep the group from getting bogged down trying to find the interesting part of the game. If you are really good at moving the group and yourself around, you can make it so that you can quickly bring the group to where the action is, especially if the group happens to be separated. Additionally, if you choose an odd specialization it's much easier for the GM to adjust one aspect of the game/world to account for that super combo you found without messing up other parts of the game.

The Power Behind the Throne

Another good way to play a really powerful character without stepping on other people is to make a character that is really powerful at making other people awesome rather than being awesome themselves. This is my preferred solution for my own power gaming tendencies. In many games, the most powerful thing you can do is buff, assist, or set up another character. If you can make everyone else in the group do +4 damage or do 7 damage yourself, then it only takes two people for the buff to be the better option. You may be able to shut down all of the enemies, so your allies can take them out easily instead of uber-killing one of them yourself. You can end up completely changing the dynamic of the game and making the whole group punch way above the weight class it should be at, but it actually helps the group dynamic. You've basically linked your being awesome with other people being awesome, so everyone wins. This also makes things easier for the GM, because usually a powergamer makes things difficult to balance between characters of different capability. You're bringing everyone up to the same level so the GM can more easily point the spotlight at people.

In-Play

Once the game has started, you can still manage your behavior to make the game better for other players. Find ways to get what you want from the game while respecting what others want. If you need to feel powerful, but someone else wants a story with drama, those desires don't have to be in conflict. Similarly, once you've made your character that has twenty different backgrounds to justify how they have their crazy powers, actually develop them as a character. If you were trained by monks, wizards, and musicians at the same time as being born of a demon mother and having blades for hands, there's got to be some sort of explanation for how and why that character exists. Give them motivations and find a way to tie them into the story in a meaningful way.

Remember that power does not always need to involve killing things and that rewards do not always need to be in the form of gold or items. When other players are roleplaying or developing the story, don't cut short their fun by just resorting to violence or throwing out some power that circumvents the interaction. Instead, be ready to act when the roleplay/story calls for you.

Humble Power

One of the big issues that can come up when you're power gaming is making other players feel inferior. If you have an insanely powerful character, shut up about it. People will figure it out in play, they don't need to have you explain why you're awesome. I have seen this happen repeatedly, with the offending player droning on as other players have their eyes glaze over. Not only is that not fun for the other players, it also eats up a large amount of time that could be spent actually playing. Tied into this is not questioning or correcting other players on how they are playing; don't expect everyone else to power game just because you do. Criticism of other people based in them not power gaming is always inappropriate. If that's not okay, then you might be in the wrong group.

Manage your Challenge

Most games are designed to operate with characters of similar capability working together. It's not fair to expect a GM to balance things around you while also maintaining a level of challenge for everyone else. If you are unwilling or unable to tone back your power gaming when creating your character, consider challenging yourself so that the GM doesn't have to. Keep yourself even with the rest of the group through personal challenges. This is fairly easy to do, maybe you can't use your highest level spells until the third round of combat, you have to take down all of your enemies with non-lethal attacks or you have to beat infiltration encounters without using invisibility. Sure you are artificially limiting yourself, but when you succeed you'll feel awesome and then if you need to, you can fall back on your reserve of uber-powers. You don't have to come up with justifications for this, but if you can in character probably other players at the table would appreciate it. You might even achieve the lofty goal of so many Method Actor players, doing something because "it's what your character would do".

Closing Thoughts

I've spend a lot of time here talking about Power Gamers (don't worry, I don't plan on doing four columns on every other type of player). It's not that they are an especially problematic type of player, just that they tend to represent one end of a certain continuum of play and so clash frequently with the players at the other end of the spectrum. Roleplaying is a big hobby, there is enough room for every type of gamer somewhere and usually at the same table. Hopefully, the big take away from all of sounds fairly obvious: Be respectful of other players, make sure everyone has a way to find fun in the game, communicate, and be willing to compromise.