Well, it's difficult to say that I've got favourite insect. But, I can say that gnat is the most interesting insect I've ever seen. 

First of all, I have to notice that this tiny insect can bring you a lot of inconveniences.

It can make a terrible noise. Which is very annoying. 

Some people try to kill gnat when they hear this noise. Well, only agile person can do it.

because, it's very complicated to catch it. Moreover it's very bad. If you try to kill gnat, imagine that you are a gnat. And someone tryes to kill YOU. I consider that you stop doing it.

To conclude I'd like to say, that it's very complicate to say that gnat is my favourite insect, but I feel a pity to gnats.