There's really only three main variations: WPA(10b last), modified WPA where 10b can be made early and good 'ol DerbyCity Bigfoot which is basically texas-express 9ball rules. There is one i left out, the horrible 10ball last-call shot/call safe version. In this turd of a game there are no two-way shots, if you miss and hook the guy he can make you shoot again. Luckily no tournament/tour of any size uses it. The NYC Predator 10b Tour used to use it and its horrible. Almost as boring as Heyball and that's saying something.