1: n. A person who plays tabletop RPGs and seeks to make the most powerful character possible, often in the form of assigning 'useless' stats such as 'charisma' very low values. Any advantage this player they can get, they are likely to take. It is not uncommon for such players to ask to start with rare items their character could or would not have obtained.
Powergamers are different from twinks in that a powergamer generally seeks to have the most powerful character without regard to the rules, while a twink seeks to manipulate the rules to gain a powerful character.
1: "God damn it ralph, you're such a powergamer, and NO, you can't start the game with a Sword of World Destruction. No. No. No... Go away!"