I knew a person who would "Acelerate" his E-6. Meaning he would hand process his film in a different first devo. I don't no what. Then he would run the film throught the rest of the E-6 process. The end results was very posterized, contrasty images.
The process was something he learned from Brooks Inst.
Then there is the cross process bunch. C-41 in E-6 and visa versa.