The tardigrade!
This is exactly the first animal I thought after reading your questing. After that I don't really have a favorite one.I guess I like the genetically altered mosquito, Anopheles gambiae, that could wipe out the entire malaria carrying species by passing on genes that cause infertility in female offspring.
"Is this ethical?" You might ask.
You could argue we're the cause of the sixth mass extinction event on this planet, so why add another species to the list? Especially considering we do not exactly know what other species, that rely on the mosquito for food, would be affected. I say, let's destroy these disease ridden buzzing bastards that were the cause of 445000 deaths in 2016 according to the WHO!
Sauce:
Wow, that's a crazy video lol I feel a little sorry for those mosquitos now...but I did read somewhere that they could disappear from earth and nothing would happen lol
I don't think that is true. Most sources speculate consequences aren't too good. There are other options however that don't kill off entire species. This video by SciShow explains it better than me: