Many players have been asking: -How can I 'fly' with hunter?-
I will explain how to vertical climb with hunter.
1. You need to back up against the wall (holding 'S' or whatever is your 'back' key)
2. Look up at angle of 85°-75°
3. Jump(not normal jump;pounce jump)
4. Don't hold your crouch button anymore (default 'CTRL')
5.While you are holding your 'back' button keep pressing pounce button (default is left mouse button)
6. Keep jumping until you reach your destination
Here is a vertical wall climb video (that is not me)

I hope that my guide helped you :D

P.S. When hunter is getting damage(shooting,explosion,burning...) he can't leap off of walls.