A plague because they've killed a lot more people in the past than hurricanes and tornados, and volcanos, and stuff. Volcano eruptions are nowhere near the worst. You can easily escape a volcano eruption. And you can easily find out when the volcano eruption will happen. Using molten rock as a defence is actually a good idea(Believe it or not) as it is straight from a volcano and so obviously has some protective qualities from heat.
And a tornado? Meh, so weak. Hardly ever actually cause any destruction. A massive gust of wind pointing straight at people side on, now that would be dangerous. But a tornado or hurricane sending wind downwards at people? All that's gonna do is push them further towards the ground.
Blizzards and sandstorms don't harm you. Unless of course you have a substance that reacts with sand badly and explodes. There are a few substances that can explode on contact with sand. Blizzards can easily be avoided. Just stay inside.
A flash flood, well pretty much everyone have something that they can float on if there's a flash flood. Just try your best to stay clear of the dangerous, sharp things, and you'll be fine. Yeah, quite a few people can die, but not as many as in a plague.
An earthquake is bad, but there are three ways to avoid it(That I can think of).
Stay outside and full body on the ground
Stay in a very strong building, and make sure there is nothing that could hurt you in the room.
Stay in the water. If you notice something dangerous flying at you, dive underwater. Unless of course, the water is infested with piranhas in which case there might be a little danger. Sharks aren't too bad. You just have to make sure you don't annoy them or have anything that smells like fish on you.