From most watched to least:
Snakes N Adders (His no BS vids are great)
Olympus Reptiles
Snake Discovery
Clint's Reptiles
Viper keeper
Reach Out Reptiles
GoHerping (I don't take him seriously. He has a way of editing his vids to be pretty fun to watch.)

Youtubers I don't care for or watch anymore due to the pet tube drama, gives out wrong advice, or seems to be collecting animals for views
Taylor Nicole Dean
Tyler Rugge
Happy Tails
Emzotic
And many others