Tactically: You'll want to use it in a Dagger, like the post above mine stated.
You get the most class versatility, with Novices, Sins, Rogues, Linkers, Swordsman classes, and others being able to use it;
You can always try different classes later on, and still have a piece of gear for them, that will aid you in leveling.
However:
Your choice should rest upon what your favorite class is. If you love GS's, then put it in a gun, plain and simple.
Most often, if you play a class you love; you'll get much less bored with it. On the flip-side, if you play a class only because
it's "Good" then you won't get nearly as much enjoyment out of it.
An easy example of this is me. I enjoy playing as a Soul linker. So instead of playing a Trans character, I worked on gearing out
my Soul linker, and I have fun basically everytime I'm on it. So it was definitely a worth while investment.