House hold pests/rodent they are so annoying
I wouldn't have created snakes,I so hate seeing them or hearing it mentioned,it could be deadly that's why,even the site of it is very scary.
I thought sure I was going to have an original answer, but apparently I don't. Mine like @divine-sound would also have to be mosquitoes. There is absolutely zero benefit to them. Now, that being said, if you are a fan of television and movies there is possibly one benefit, but I will get to that in a second.
Besides buzzing and being annoying and drinking your blood and making you itch, lets look at the movie Jurassic park. Everyone thinks that dinosaurs were the main bad guy in that movie, but quite honestly I say it was the mosquitoes. If they had never found that mosquito in amber then none of the horrible things would have happened.
The one thing I can see mosquitoes being good for is the carrying of beneficial treatments. Take a look at the tv show Zoo for example. As a solution for one of the seasons they were looking at using mosquitoes to transmit the cure for the DNA disease that was plaguing mankind. That is about the only good thing I could see about them. I have to believe that somewhere along the line God in their infinite wisdom has a plan for mosquitoes we just haven't figured it out yet. Until then, they can bugger off and stop ruining my camping trips.
I have a strong objection against its creation by God. I also don't see any role of Mosquito in balancing the ecosystem of the Nature. If you see every other creature, then you may notice that all of them have a definite and a distinct role. Even the snake which is a poisonous one has a role in balancing this ecosystem, but a mosquito is simply a worst burden on Earth and it has harassed every other creature. Several deadly dieseases are due to mosquitoes. It is not just a case for human being. Everyone is worried due to mosquito. The pet animals also suffered a lot due to mosquito.
In humid regions, Mosquitoes are not less than a terror. So I must ask God for what reason Mosquito was created and why the reproduction system has been designed for mosquitoes in such a way that they can multiply in tremendous numbers as a female mosquito can lay hundreds of eggs at a time. That is really deadly. If you check the stat of WHO, then you will be surprised to know that millions are exposing to risk of death every year due to deadly viruses carried by the mosquitoes. So God should review the creation of mosquitoes again and if possible God should make necessary arrangement so that mosquitoes become extinct in this Earth.
I God probably would never have created man. From him only one harm to nature and the environment.