Hmm, as for insects, I actually am really afraid of flies, but they're interesting to be seen drawn. Should I link pictures? I mean, my stuff is very generic.
For mammals, I love maine coons, they are a beautiful sort of cat.
Birbz~ Flamingos are wack and neat
And for fish, tilapia, because they taste good. OR for something that looks good, I think lampreys are interesting.

I hope someone else comments too, so you have more options.