Boomerang has been in the Zelda series since the beginning. It's a decent weapon(depending on the game) but is pretty much an optional weapon(depending on the game).
Which one is the best?
We'll define boomerang as a weapon that can grab items annd bring it back to you only. Soon Beetle will be allowed, but hookshot, whip, etc will not.
Also only the best upgrades. So a LV1 boomerang will not count.
I choose FSA. It helps you collect Force Gems(which are required) and let's you be a real jerk against your friends. "Hey get back here"(uses boomerang )
It's the only Zelda game where I'm really happy to get the boomerang.
Hmmm... Where's TP? I liked that boomerang. Not only was it a boomerang, but it had the Fairy of Winds. I also liked TWW's boomerang because stunning enemies is extremely useful and OoT's boomerang was nice because I hardly had to use my slingshot anymore (and didn't have to worry about the deku seeds) and I could collect the far-off gold skulltulla tokens.
If you count the beetle as a boomerang, it wins in some aspects. The gale boomerang was awesome as well. It also matters what boomerang in some cases. Like in the Minish cap you had a regular one and you could get a magical one. Now if you just included regular boomerang's, it'd have to be on what they could do that would judge them Anyway, if you count the beetle as one, it was likely my favorite. It could pick up objects and scare bad guys. And you could use it just to get a better view of things. It didn't have an enabled targeting system like boomerangs did though...
That boomerang was great in combat for stunning enemies who liked to block a lot. Plus it was quick to use and normally went straight for your target instead of circling around. It also was quick to switch between your sword and boomerang too.
Born to fight
Trained to kill
Ready to die
But never will
Hmm, TWW has a commanding lead, eh? I wish I remembered more of that game and its boomerang, but my TWW disc is borked. Anyway, out of the games I've played multiple times and have a pretty good memory for, Twilight Princess' would be the best to me. You've got precision IR aiming, it locks onto stuff, what's not to like?
The opening post mentioned usefulness. The boomerang is your friend in LoZ. I can't remember if it'll stun a Wizzrobe (and if I'm remembering right it won't stun a darknut), but it definitely stuns a lot of stuff and even kills Keese and such. It moves in 8 directions too, which is really good for the four-direction-walking Link. I guess I think it's the most useful, but even so I voted TP.
The original LoZ had the best boomerang in that it traveled fast, you could throw it almost any direction including behind you, and it was almost an essential part of combat. The boomerang in Wind Waker did a great job transitioning the boomerang to a 3d environment and the homing feature was boss but I never felt it was as essential as it was in LOZ.
I liked Wind Waker's system, where many things could be 'z-targetted' at once by the boomerang and then released to fly on its own. I remember it had some pretty interesting uses in solving puzzles as well, getting the boomerang to swirl-a-doo a certain path before it ran out of string.