You don't? Isn't he one the first you meet when starting this game?
Gunnar is at Bareshade on Mondays, Wednesdays, Fridays and Sundays. You can encounter him at the masturbation spot (caravan), tavern when you are whoring for clients (harold's quest), he can appear at Torben's house, visits Bernard's shop when you offered to help out Bernie, at the fair when strolling around and watch fireworks with him.
He's at Northcrest on Tuesdays, Thursdays and Saturdays. You can encounter him at residential area when roaming around, and at the public bath at the inn.
Lastly you'll always meet him when you wait at River's Bank and if your Bandit's Camp's morale is low(er than 25) then you can also find him at the road/track between your house and Bareshade.
I think these were all the options where you can find him.