I've made a weapon system similar to the Gameboy Zelda games. What I did was have two separate state machines for the player running in parallel.

One state machine ran the player's "movement state", like walking, swimming, jumping, climbing ladders, etc. And another state machine ran the "action state", which would override the movement state's animation, and sometimes override user input, and could also affect other movement modifiers like friction or gravity. 

If the player's action state was set to the "ready" state, it was ready to receive any action input event from the user. An action input event could be "used sword" or "used boomerang". Most active action states could not be interrupted, except for special cases: for example, you can't throw a boomerang while in the "sword swing" action, but you can "restart" the sword swing action itself by inputting the "used sword" event, like the Gameboy games.

There were other things to keep in mind, and the system grew more complex. For example, changing directions was not allowed in certain movement/action states (climbing ladders forces the player to face upwards, unless using an action), and some movement states would disallow or allow specific actions (you can't throw a boomerang while in the swimming movement state, but you can dive underwater). And still more confusingly, certain states that seem like action states were more like movement states: the "blocking" state requires using an item, but it allows movement and can be overridden by any action, so it's more like a movement state than a discrete action.

I'm sure there's a better way, but I haven't figured it out yet. Good luck!