The closest I had was a massive thunderstorm passing over the house and I was stood in the porch watching, with loads of lightning going off all around. Then a strike hit right around me, whether it was the trees in front of the house or something else close I've no idea, but the world just went white, bright white. Your eyes close instinctively, but it didn't matter, I could see straight through my eyelids and the world looked like an overexposed negative! and whether it was to do with a concussive wave or just a body reaction but it blew me off my feet and I ended up in a dazed crumpled heap at the bottom of my stairs. The thunderclap that accompanied it was biblical!
Gf at the time was in the lounge crying hysterically and it was all quite surreal coming around from the daze, with your eyes trying to readjust and car/house alarms going off, pretty epic experience really