It's tough to say, but probably May 4, 2002, near Vick, TX. Amos and I had gotten ourselves way up in the notch as the storm was undergoing a transformation, and the hail core essentially developed around us. We were pounded with baseballs for what seemed like an eternity as we tried to escape. On the plus side, we witnessed a brief tornado shortly thereafter. The windshield was in pretty bad shape, but held well enough to where we could continue chasing. We caught the Happy, TX tornado the next day.
Luckily, I managed to avoid hail on April 5, 2003. I blasted through Woodson at 80 mph (literally) only a minute or two before the place was decimated. It remains one of the scariest moments of my chase career - the inflow was incredible, with trash cans and lawn chairs flying across the road in front of me, and the hail was nipping at my heels. I actually hit a trash can and dragged it halfway through town with me - I was worried I'd have to stop and remove it manually (losing precious time), but a quick swerve on to the rough shoulder knocked it loose. I just wanted to get the hell outta there.
After hearing the radio traffic from those behind me who weren't lucky enough to make it out in time, I just about broke off the storm. I didn't get close to the updraft again until somewhere in Parker County. I didn't want to take my chances with that hail core again, especially not in the hills of Palo Pinto County.