All fighting styles used by SetPlayerFightingStyle and GetPlayerFightingStyle are listed below.
It should be noted that the term "fighting style" is actually incorrect - the IDs used by SA-MP and UG-MP are actually referred to as (melee) combo types by R*, and are also used in singleplayer.
These so-called combo types are not just used for fighting styles - all melee weapons have one. Their IDs are defined in the data files (but are hardcoded on stock GTA: SA), and correspond to a combo type name.
The combo type name, is then used as an identifier for melee weapon statistics. This means that, as you might have noticed, the fighting styles are all combo types, and kindof are treated as any other melee weapon.
Now, sure, this is all interesting, but combo types are simply irrelevant to server developers, as the only use case in SA-MP/UG-MP is the so-called fighting styles. We will therefore only list the available fighting styles. We are considering to give server developers the ability to modify (melee) weapon statistics in a future UG-MP update though (if that's even possible), which means the fighting style constants would become depricated.