We're having the same problem with a glass cabinet that we have. I have done all the same things you have done. Ds knows he's not supposed to hit it hard, but sometimes he still does. I just try to keep consistent every time, telling him that he can hit the floor or the couch, but not the glass, and then show him. It's doesn't always work, but I'm hoping that eventually he will start to understand.
We have a big problem with the glass shower doors. Every time we are in the bathroom, he grabs them, opens it up a little ways and then shakes it. Not only has he made it come off the track, but the track is actually getting bent, and I am afraid the door will break one of these times. I keep telling him he can't do that, he will get hurt, glass will break, etc. etc. But like you said, he likes the sound it makes.
Regarding the stove knobs, we actually just took the knobs off. I keep them next to the stove, and I just put one on to turn the stove on and then take it off again. The knob guards didn't work for us cuz the knobs were too big. Taking them off works great.
So, I guess I don't really have the solution to the windows. Just that hopefully they will give up before you do!