Kingroot, KingoRoot, framaroot, and towelroot. Framaroot and towelroot works only for Kitkat and below. Kingroot and KingoRoot works well for OS like Lollipop below. Because if you're on Marshmallow only limited devices are supported, you can look for the list of the supported devices on their respective websites. Also, if you want to root Marshmallow. You'll have to unlock your bootloader first.