Is there a EntityPlayer instance? not EntityClientPlayerMP, EntityPlayerSP or EntityPlayerMP but one for the basic EntityPlayer?

Possibly, but probably not specifically.

All of those are instances of EntityPlayer, so, kinda.

Why?

Nevermind I think I need to use datawatchers for doing it...

There's one for MP which you should be using for each player in a game/lan.

 

MinecraftServer minecraft = FMLClientHandler.instance().getServer();
		String allNames[] = minecraft.getAllUsernames().clone();
		for(int i = 0; i < allNames.length; i++) {
			EntityPlayerMP player = minecraft.getConfigurationManager().getPlayerForUsername(allNames[i]);
		}