This character has the I Just Want to Be Special attitude, but the kind of "special" he wants to be is a gunfighter. What distinguishes the Wannabe from the Young Gun is that the latter usually just needs some training/experience/maturity to get up to speed, whereas the Wannabe lacks the talent or temperament to succeed as The Gunslinger.

He may have plinked cans in the backyard, and practiced his fancy draw in the mirror, but the Wannabe doesn't have the speed and accuracy he thinks he does. And he's going to challenge a real gunfighter just as soon as he gets up the nerve. This will not end well.