If you beat the game and choose to replay the game with the same character, your character type will be able to learn some skills he or she would otherwise be unable to learn. For instance, on a second play-through, Adepts can learn to use Shotguns, First Aid, and other skills they were otherwise unable to use the first time through.
Higher Levels
You can increase your maximum level from 50 to 60 if you beat the game once through and opt to use your character from the previous game in a new game.
Play Again
After beating Mass Effect, you can play through the game again, with the same character, same skills, items, et cetera.