The boomerang idea is great, it can be a terrifying thing to use (I\'m an Auzzie too

).
I\'m no expert on them of course I just remember as a kid playing with one, it was a heavy thing to use but glided through the air with a heavy whoosh sound. They can be quite scarey to use too. I\'ll never forget my brother being hit by one though, considering the type of boomarang its lucky he has a hard head

. Which isn\'t so funny really the next time it hit a tree breaking a thick branch off (it would have killed someone if it connected) I guess its all in the throw.
The longer sided boomerang spoken about earlier is a non-returning design. The traditional returning design is a curved or v shape.
There are also sports boomerangs that have more 3 blades or more or hooked edges. Called hook, twister etc and so forth whatever name the company wants they could be interesting too... especially the use of lead weights etc to a traditonal weapon.
Also the returning of a boomerang is not always certain, mostly it comes down to the way it is thrown, requiring a twist of the wrist on release.
My point besides supporting the creation of such a weapon or a weapon based on the boomerang is to say it has various forms and uses worth investigating.
I saw earlier the mention of a Bola, a weapon I recognise and would also like to see. Its sole purpose is to entangle and bring down a beast/target. While not a lethal weapon its uses could be interesting in capturing of targets and may cause damage to legs

slowing targets.
As for the yo-yo... I don\'t think there is a simple answer to its origin for instance it can be found throughtout the world in various forms. In China about 1000 BC (Diabolo), greece around 500 bc (a delicate ceramic design similar to todays types). One thing is for certain they are all toys. In the Philippines it may have had origins as been a weapon. But besides the physics of the oversized yo-yo casting it immediately under a suspicious light it would appear \'the weapon origins\' may have been a marketing campaign around the 1930\'s - 1940\'s.
The name yo-yo is from Tagalog (the main language in the Philippines) and there is no doubt the yo-yo toy we know has its origins there, by this I mean the inclusion of looping the string around the axle allowing the yo-yo to rest at the end of the string. Anyway my point is, ditch the name, its the name of a kids toy. However use the concept and design your own, work out if its a blunt or spiked weapon and write it up etc
My poorly constructed example :
Name : Devils (<- maybe replace with appropriate creature in planeshift like \'Tremor\' or what have you) Tongue
Description : A hand sized loop with a strong chain attacted connected at the other end to a spindle inside an outer two halved shell. The outer shell is attached to the spindles sides and curves around most of the spindle itself, leaving only a slightly larger then chain width opening for the chain. The hand loop attaches into a slot along the chain opening ( where the chain is wrapped around ) and clicks into a simple locking mechanism. Thus weapon is carried \'locked\' looking like a loop connected to a spiked or bladed ball. In more elaborate designs the spikes/blades are retracted until the chain unlockes, also larger designs have the hand inside the ball holding a bar.
Use : If a strong enough force, such as a throw action occurs the locking mechanism releases and the ball can unwind. If used correctly the ball flies at its target bludgeoning them and if bladed slicing them. The weapon now acts as a ball and chain (if you\'ve ever seen \'Salute of the Jugger\' you\'ll know how effective a chain can be when swung, then add in a ball full spikes/blades

. Anyway it can also be used to disarm targets (wrap around a sword/axe and pull it away) or entangle legs or choke if skilled enough. After combat it is wound back up and locked.
Pros : easy to carry, range, ability to disarm/entangle.
Cons : hard to use, in most cases effective against one target only. Wound up after combat, takes time.