Admiral:
This generic magic weapon is the brainchild of my brother. Let’s test its waters and see if we can reach good and simple rules, wording and points cost.
I’ve never been good with rules, so please help out if you can. 
Kureshian Boomerang ???pts
Throwing weapon, strength as user. Use teardrop template and ignore the template’s inside. Each model touched by its edge must pass an Initiative test or get hit.
Dînadan:
How about instead making it hit like a bolt thrower, i.e. It still follows the curved path, but instead of rolling to hit each individual model, you roll once to hit and then it keeps on going until it fails to kill (either up the strength so it follows the -1S each additional hit part of the bolt thrower rules or make it staying at user’s Strength an exception to where it follows the Bolt Thrower rules).
Bloodbeard:
The boomerang will come back to the thrower no matter what, so no need for BS. How about forcing all hit models to take an initiative test or get hit on the head?
Admiral:
@Dînadan: Nice idea. I had also thought about it, but since it’s such a low strength weapon except for in the hands of an Ogre, having it work like a ballista wouldn’t make it too useful.
@Bloodbeard: That’s a great idea! My brother also likes it. First post updated.
What about points cost? I’ve no idea how one would price this kind of thing. Would 30 pts be too high?
Dînadan:
Well it is a magic boomerang so maybe have it at a constant Strength or start at double user’s strength? 
How about making a Kureshian Mercenary unit all armed with mundane boomerangs that work on users strength as I described in my last post and then the magic version working as above in this post?
Admiral:
Well it is a *magic* boomerang so maybe have it at a constant Strength or start at double user's strength? ;)That's a good idea, although I expect it to be tricky to handle in games. It's worth testing. I'll tell my brother :)
How about making a Kureshian Mercenary unit all armed with mundane boomerangs that work on users strength as I described in my last post and then the magic version working as above in this post?
Dînadan