Golf ball-sized hail. Intense, gusting wind smashing the ground and spreading out, pushing everything in its way. Torrential downpour making it impossible to see anything farther than an inch away. My god, microbursts are previews for the apocalypse.
A burst like that hit the Long Island Sound once. It destroyed a bunch of small boats. My uncle was out alone on his boat. He got the jib down fast enough, but the high wind hit while he was trying to get the mainsail down. It broke his mast (a giant wooden one, probably around 50 ft tall).
Luckily he made it through ok. I believe there were a couple of deaths in that storm, and a number of boaters needed to be rescued. I have been in a boat in other storms, it sounds absolutely horrifying to be out in an event like that though.