it is a toss up: was in miami during Floyd, so that gets "seen it" points...but for some inexplicable reason, andrew is my favorite...& Bill... I don't know: asking this is like asking "what's your favorite word". as for tornadoes, i don't have a fave, (though I love waterspouts)but i gotta say lightning is the best part (i actually have, like many atmospheric physicists, a photo album composed entirely of pictures of storms and lightning)
are you asking from a scientific viewpoint or a personal point? I love storms as a scientist, but as a person,i hate seeing the destruction they leave in their wake... good people are affected by awesome thing in bad ways.