Open Category -- Like B-western but without dress requirements. Able to shoot any style on any stage. Any legal gun/gear.
My list then would be:
Style Categories:
Open - shoot anything, any way.
Duelist - if you want to only compete against the 1 handers
GF - if you want to only compete against the other GF
Equipment Modifiers (may modify the Styles above)
Cap - if you want to only compete against the other Cap & Ball folks
Power Factor - 140+ power factor, compete against the other big boomers.
Black Powder - compete