Tip: Take advantage of easy to install Patches in your hack. The No More Sprite Tile Limits or SA-1 patches should be considered if you're encountering glitches where Mario and/or sprites are turning invisible.
The Blue Boomerang from Super Mario Advance 4's e-Reader levels.
It can be picked up and thrown, and it will kill enemies in a similar way to a thrown shell. It cannot be thrown up or placed back down once it's been picked up.
Additionally, it includes an updated Boomerang Bros. sprite which will throw a new Extended Sprite -- it functions similarly to the existing sprite, but it will turn into the carriable Blue Boomerang once the Boomerang Bros. that threw it is defeated.
If you're using my other Boomerang Bros. sprite, you can replace it with this version and it should work without issue.
Added lorom and sa1 tags. Fixed a missing SA-1 conversion.
It's definitively a sprite which you can create cool levels. I just wish you're able to just place the boomerang down instead of always throwing it.
One thing to note: Aside from a missing SA-1 conversion, I also have noticed that you're storing to an unused address as well as load from an uninitialised one. That could lead to unintended behaviour but since I haven't found any... but please consider to fix it next time!