I had one I was really scared of when I worked at a pet shop. It was a huge nile monitor and the thing just went crazy everytime it saw me. When other people were around it was calm and normal (couldnt touch it) but when I came around it unleashed the gates of hell on its enclosure. It was crazy.
"Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us."