Ten little facts about Dean
He was baptized an evangelical.
As a child, he loved playing with the soldiers and guns John gave him, and the dolls and pram Mary gave him. And he loved it when his Omega mom painted his nails a different color each time.
He eats what the world calls "American food" - fast food, frozen convenience foods, vending machine meals, and anything you can buy at a gas station. And being an Omega, he is wary of unfamiliar foods unless he gets them from his Alpha (John, Castiel, or Bobby). But this is very much influenced by his age. As an adult, he'll be much more open to trying new things.
He is good at shooting at moving targets and has a high percentage of hits. He's not very good at long range shooting and has a relatively low percentage of lethal hits.
He is agnostic - if he were to ponder the meaning of life, he would be willing to acknowledge the existence of a higher power, but would never be willing to practice a religion.
He is much smarter and has a much greater general outlook than those around him think. Partly he deliberately pretends to be a "stupid Omega" and partly he thinks he is not smart enough to understand anything more complex.
He's grown an inch in the time he's known Castiel. And he hasn't stopped growing.
He fell in love with Castiel because he is very much like his father John -- a smoker, a drinker, a taciturn and quiet type who prefers to keep to himself, and very dangerous when he wants to be or when he loses his temper.
For an Omega, he has unusually high levels of testosterone and alpha enzymes, which affects his appearance and behavior, as well as his smell. He produces less of certain components of the pheromone spectrum, and they happen to be the same ones that bother Castiel. That's why it's the only Omega that smells good to Castiel. Thirty years ago, this "hormonal deviation" of Dean's would have been considered a disorder affecting the Omega male's appearance, behavior, and especially fertility, and his parents would have been recommended hormonal and psychological treatment.
He had always wanted tattoos and piercings, but had not yet had the time to get them or to commit to getting his earlobe pierced.