To jump I’m just adding velocity on the y-axis, but my character gets stuck on straight walls
Not trying to sound rude, but how do you expect anybody to help you given that little information?
The approach you explained with half a sentence should work, so the problem is hidden in your specific way of implementing it. To say more, we’d at the very least have to see some code.
As posting information properly is always important, this is worth a read in any case: How to report a problem in the Unity3D forums – PLBM Games
Hey, its because of the default physics material. Try creating a smooth physics material and adding to to both the object jumping and the object it is colliding with.