When you're taken, he often is the best guy friend.
When you're dating a loser, he breaks you both up.
When there's trouble, he's the big brother.
When you're single, he will often date you as long as you have no one. Occasionally can turn into very intense flirting.
Can be sexy, kind, funny, talented, stylish, passionate, romantic, even adoring or very attractive.
Quite often is charming and extremely kind but has a low chance of being married due to a complex issue in his life.
Every girl needs a multi-purpose best boy.
Boy: I'll kick his ass! You just go get dressed up pretty and we'll go to the mall. When your ex is around, you can be clingy to make him jealous! Deal, sweets?
Girl: Oh yeah! I'll make sure I look really nice for him to see us in public!*I love my multi-purpose best boy!*
Boy: That's better! I'll spike my hair so we look good together. Hold on babe. :D
Girl 2: OMG! I need a guy like that!!!
Boy: I'm her multi-purpose boy so I'm taken!