The highest I've climbed is in the P-80 to about 37,000ft. I stall it there at about a 10 degree angle of attack, and dove at about 70 degrees back down. It was cool, I reached about 650 mph (Almost there!). I managed to pull out at 100ft going around 600 mph. It was fun.

I got just under that in a P-47, 35,000. Although I'm pretty sure the ceiling on that bird is 40,000ft.
