Jack

Jack is an adult pony who does not have his cutie mark, not for the lack of trying though. His name comes from the phrase 'Jack-of-all-Trades'
And like his name he tends to have skills lying in many areas, but no real talent for one.
To make his living he does odd jobs around the town, whatever he can to help him get his cutie mark, eventually...
Jack has to be kind of a smooth talker
He needs this skill in order to convince the ponies to pay him for the service, rather than going to someone who has the skill/cutie mark for it.

For personality he tends to be the witty one, making jokes and all around just trying to be entertaining. Though he does have a slight insecurity for not having his cutie mark, he's learned to live with it for the time being.