His training is as a ranger and has developed his skills to fit the city. His fighting style is skirmish fighting using improvised weapons and ambush attacks. He is often ignored in the city or mocked but he uses this to track his targets. Ambushing from cover and dealing with them in a secluded spot.
This is a good character to harass a party with even if he does not serve as a combatant. He could be tracking an spying on the party for some noble, only to alert guards later on. If discovered he could turn the pursuit into an elaborate game. Continuing the jest while he batters the party with jugs or wine bottles for comedic effect.
The jester can also serve as a good bridge between the underbelly of crime and the upper echelons of society. Making him a Mr. Johnson stand in for the fantasy setting.